20931840 has 216 divisors, whose sum is σ = 76527360. Its totient is φ = 5271552.

The previous prime is 20931809. The next prime is 20931877. The reversal of 20931840 is 4813902.

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 23 ways as a sum of consecutive naturals, for example, 264921 + ... + 264999.

Almost surely, 2^20931840 is an apocalyptic number.

20931840 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 20931840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38263680).

20931840 is an abundant number, since it is smaller than the sum of its proper divisors (55595520).

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

20931840 is a wasteful number, since it uses less digits than its factorization.

20931840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 129 (or 112 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 27.

The square root of 20931840 is about 4575.1327849583. The cubic root of 20931840 is about 275.5936047971.

The spelling of 20931840 in words is "twenty million, nine hundred thirty-one thousand, eight hundred forty".