21662640 has 100 divisors (see below), whose sum is σ = 75260064. Its totient is φ = 5774976.

The previous prime is 21662633. The next prime is 21662653. The reversal of 21662640 is 4626612.

It is a happy number.

21662640 is a `hidden beast` number, since 2 + 16 + 6 + 2 + 640 = 666.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 4809 + ... + 8151.

Almost surely, 2^21662640 is an apocalyptic number.

21662640 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 21662640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37630032).

21662640 is an abundant number, since it is smaller than the sum of its proper divisors (53597424).

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

21662640 is a wasteful number, since it uses less digits than its factorization.

21662640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3368 (or 3353 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 21662640 is about 4654.3141277744. The cubic root of 21662640 is about 278.7642823492.

The spelling of 21662640 in words is "twenty-one million, six hundred sixty-two thousand, six hundred forty".