21001662 has 48 divisors (see below), whose sum is σ = 50354928. Its totient is φ = 6272640.

The previous prime is 21001657. The next prime is 21001667. The reversal of 21001662 is 26610012.

It is a happy number.

21001662 is a `hidden beast` number, since 2 + 1 + 0 + 0 + 1 + 662 = 666.

It is an interprime number because it is at equal distance from previous prime (21001657) and next prime (21001667).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 13728 + ... + 15180.

It is an arithmetic number, because the mean of its divisors is an integer number (1049061).

Almost surely, 2^21001662 is an apocalyptic number.

21001662 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 21001662, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25177464).

21001662 is an abundant number, since it is smaller than the sum of its proper divisors (29353266).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21001662 is a wasteful number, since it uses less digits than its factorization.

21001662 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1545 (or 1542 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 18.

The square root of 21001662 is about 4582.7570304348. The cubic root of 21001662 is about 275.8996957508.

Adding to 21001662 its reverse (26610012), we get a palindrome (47611674).

The spelling of 21001662 in words is "twenty-one million, one thousand, six hundred sixty-two".