21151746 has 64 divisors (see below), whose sum is σ = 58613760. Its totient is φ = 5492880.

The previous prime is 21151733. The next prime is 21151747. The reversal of 21151746 is 64715112.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21151747) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1615 + ... + 6701.

It is an arithmetic number, because the mean of its divisors is an integer number (915840).

Almost surely, 2^21151746 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21151746, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29306880).

21151746 is an abundant number, since it is smaller than the sum of its proper divisors (37462014).

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

21151746 is a wasteful number, since it uses less digits than its factorization.

21151746 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5116 (or 5110 counting only the distinct ones).

The product of its digits is 1680, while the sum is 27.

The square root of 21151746 is about 4599.1027385785. The cubic root of 21151746 is about 276.5553562648. Note that the first 3 decimals are identical.

Adding to 21151746 its reverse (64715112), we get a palindrome (85866858).

The spelling of 21151746 in words is "twenty-one million, one hundred fifty-one thousand, seven hundred forty-six".