21704920 has 64 divisors (see below), whose sum is σ = 52682400. Its totient is φ = 8017920.

The previous prime is 21704887. The next prime is 21704933. The reversal of 21704920 is 2940712.

It is a super-2 number, since 2×21704920² = 942207104412800, which contains 22 as substring.

It is a congruent number.

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 15 ways as a sum of consecutive naturals, for example, 39850 + ... + 40390.

Almost surely, 2^21704920 is an apocalyptic number.

21704920 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 21704920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26341200).

21704920 is an abundant number, since it is smaller than the sum of its proper divisors (30977480).

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

21704920 is a wasteful number, since it uses less digits than its factorization.

21704920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 628 (or 624 counting only the distinct ones).

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 21704920 is about 4658.8539363238. The cubic root of 21704920 is about 278.9455236367.

The spelling of 21704920 in words is "twenty-one million, seven hundred four thousand, nine hundred twenty".