21162640 has 40 divisors (see below), whose sum is σ = 49659768. Its totient is φ = 8386560.

The previous prime is 21162623. The next prime is 21162641. The reversal of 21162640 is 4626112.

It can be written as a sum of positive squares in 4 ways, for example, as 112896 + 21049744 = 336^2 + 4588^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a hoax number, since the sum of its digits (22) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21162641) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7870 + ... + 10210.

Almost surely, 2^21162640 is an apocalyptic number.

21162640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21162640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24829884).

21162640 is an abundant number, since it is smaller than the sum of its proper divisors (28497128).

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

21162640 is a wasteful number, since it uses less digits than its factorization.

21162640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2467 (or 2461 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 21162640 is about 4600.2869475719. The cubic root of 21162640 is about 276.6028271601.

Adding to 21162640 its reverse (4626112), we get a palindrome (25788752).

The spelling of 21162640 in words is "twenty-one million, one hundred sixty-two thousand, six hundred forty".