21553530 has 32 divisors (see below), whose sum is σ = 53979264. Its totient is φ = 5497536.

The previous prime is 21553529. The next prime is 21553531. The reversal of 21553530 is 3535512.

It is an interprime number because it is at equal distance from previous prime (21553529) and next prime (21553531).

It is a self number, because there is not a number n which added to its sum of digits gives 21553530.

It is not an unprimeable number, because it can be changed into a prime (21553531) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14929 + ... + 16308.

It is an arithmetic number, because the mean of its divisors is an integer number (1686852).

Almost surely, 2^21553530 is an apocalyptic number.

21553530 is an abundant number, since it is smaller than the sum of its proper divisors (32425734).

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

21553530 is a wasteful number, since it uses less digits than its factorization.

21553530 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31270.

The product of its (nonzero) digits is 2250, while the sum is 24.

The square root of 21553530 is about 4642.5779476493. The cubic root of 21553530 is about 278.2954693693.

The spelling of 21553530 in words is "twenty-one million, five hundred fifty-three thousand, five hundred thirty".