21557040 has 40 divisors (see below), whose sum is σ = 66827568. Its totient is φ = 5748480.

The previous prime is 21557033. The next prime is 21557047. The reversal of 21557040 is 4075512.

It is an interprime number because it is at equal distance from previous prime (21557033) and next prime (21557047).

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

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 21557040.

It is not an unprimeable number, because it can be changed into a prime (21557047) 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, 44671 + ... + 45150.

Almost surely, 2^21557040 is an apocalyptic number.

21557040 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21557040 is an abundant number, since it is smaller than the sum of its proper divisors (45270528).

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

21557040 is a wasteful number, since it uses less digits than its factorization.

21557040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89837 (or 89831 counting only the distinct ones).

The product of its (nonzero) digits is 1400, while the sum is 24.

The square root of 21557040 is about 4642.9559549925. The cubic root of 21557040 is about 278.3105753879.

The spelling of 21557040 in words is "twenty-one million, five hundred fifty-seven thousand, forty".