21540120 has 64 divisors (see below), whose sum is σ = 73854720. Its totient is φ = 4923264.

The previous prime is 21540083. The next prime is 21540157. The reversal of 21540120 is 2104512.

It is an interprime number because it is at equal distance from previous prime (21540083) and next prime (21540157).

It is a super-2 number, since 2×21540120² = 927953539228800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21540120.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11982 + ... + 13661.

It is an arithmetic number, because the mean of its divisors is an integer number (1153980).

Almost surely, 2^21540120 is an apocalyptic number.

21540120 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21540120 is an abundant number, since it is smaller than the sum of its proper divisors (52314600).

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

21540120 is a wasteful number, since it uses less digits than its factorization.

21540120 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25664 (or 25660 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 15.

The square root of 21540120 is about 4641.1334822433. The cubic root of 21540120 is about 278.2377415249.

Adding to 21540120 its reverse (2104512), we get a palindrome (23644632).

The spelling of 21540120 in words is "twenty-one million, five hundred forty thousand, one hundred twenty".