21700656 has 80 divisors (see below), whose sum is σ = 62853120. Its totient is φ = 7168320.

The previous prime is 21700649. The next prime is 21700667. The reversal of 21700656 is 65600712.

21700656 is a `hidden beast` number, since 2 + 1 + 7 + 0 + 0 + 656 = 666.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

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

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 82381 + ... + 82643.

It is an arithmetic number, because the mean of its divisors is an integer number (785664).

Almost surely, 2^21700656 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21700656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31426560).

21700656 is an abundant number, since it is smaller than the sum of its proper divisors (41152464).

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

21700656 is a wasteful number, since it uses less digits than its factorization.

21700656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 471 (or 459 counting only the distinct ones).

The product of its (nonzero) digits is 2520, while the sum is 27.

The square root of 21700656 is about 4658.3962905704. The cubic root of 21700656 is about 278.9272558644.

The spelling of 21700656 in words is "twenty-one million, seven hundred thousand, six hundred fifty-six".