21587920 has 40 divisors (see below), whose sum is σ = 50387400. Its totient is φ = 8601600.

The previous prime is 21587893. The next prime is 21587921. The reversal of 21587920 is 2978512.

It can be written as a sum of positive squares in 4 ways, for example, as 6190144 + 15397776 = 2488^2 + 3924^2 .

It is a tau number, because it is divible by the number of its divisors (40).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21587921) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 35620 + ... + 36220.

It is an arithmetic number, because the mean of its divisors is an integer number (1259685).

Almost surely, 2^21587920 is an apocalyptic number.

21587920 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21587920 is an abundant number, since it is smaller than the sum of its proper divisors (28799480).

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

21587920 is a wasteful number, since it uses less digits than its factorization.

21587920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1063 (or 1057 counting only the distinct ones).

The product of its (nonzero) digits is 10080, while the sum is 34.

The square root of 21587920 is about 4646.2802326162. The cubic root of 21587920 is about 278.4434033047.

The spelling of 21587920 in words is "twenty-one million, five hundred eighty-seven thousand, nine hundred twenty".