20931920 has 80 divisors (see below), whose sum is σ = 52496640. Its totient is φ = 7736832.

The previous prime is 20931917. The next prime is 20931941. The reversal of 20931920 is 2913902.

It is a tau number, because it is divible by the number of its divisors (80).

It is a self number, because there is not a number n which added to its sum of digits gives 20931920.

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 15 ways as a sum of consecutive naturals, for example, 71294 + ... + 71586.

It is an arithmetic number, because the mean of its divisors is an integer number (656208).

Almost surely, 2^20931920 is an apocalyptic number.

20931920 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 20931920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26248320).

20931920 is an abundant number, since it is smaller than the sum of its proper divisors (31564720).

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

20931920 is a wasteful number, since it uses less digits than its factorization.

20931920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 372 (or 366 counting only the distinct ones).

The product of its (nonzero) digits is 972, while the sum is 26.

The square root of 20931920 is about 4575.1415278656. The cubic root of 20931920 is about 275.5939558964.

The spelling of 20931920 in words is "twenty million, nine hundred thirty-one thousand, nine hundred twenty".