21290920 has 32 divisors (see below), whose sum is σ = 54748800. Its totient is φ = 7299648.

The previous prime is 21290903. The next prime is 21290921. The reversal of 21290920 is 2909212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21290921) by changing a digit.

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, 37740 + ... + 38299.

It is an arithmetic number, because the mean of its divisors is an integer number (1710900).

Almost surely, 2^21290920 is an apocalyptic number.

21290920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21290920 is an abundant number, since it is smaller than the sum of its proper divisors (33457880).

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

21290920 is a wasteful number, since it uses less digits than its factorization.

21290920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 76057 (or 76053 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 25.

The square root of 21290920 is about 4614.2084911716. The cubic root of 21290920 is about 277.1605892829.

The spelling of 21290920 in words is "twenty-one million, two hundred ninety thousand, nine hundred twenty".