21906985920 has 56 divisors (see below), whose sum is σ = 69554683344. Its totient is φ = 5841862656.

The previous prime is 21906985897. The next prime is 21906985943. The reversal of 21906985920 is 2958960912.

It is an interprime number because it is at equal distance from previous prime (21906985897) and next prime (21906985943).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11408929 + ... + 11410848.

Almost surely, 2^21906985920 is an apocalyptic number.

21906985920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21906985920 is an abundant number, since it is smaller than the sum of its proper divisors (47647697424).

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

21906985920 is a wasteful number, since it uses less digits than its factorization.

21906985920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22819797 (or 22819787 counting only the distinct ones).

The product of its (nonzero) digits is 699840, while the sum is 51.

The spelling of 21906985920 in words is "twenty-one billion, nine hundred six million, nine hundred eighty-five thousand, nine hundred twenty".