21524640 has 48 divisors (see below), whose sum is σ = 67804128. Its totient is φ = 5739776.

The previous prime is 21524623. The next prime is 21524647. The reversal of 21524640 is 4642512.

It is a tau number, because it is divible by the number of its divisors (48).

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 21524640.

It is not an unprimeable number, because it can be changed into a prime (21524647) 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, 21942 + ... + 22901.

It is an arithmetic number, because the mean of its divisors is an integer number (1412586).

Almost surely, 2^21524640 is an apocalyptic number.

21524640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21524640 is an abundant number, since it is smaller than the sum of its proper divisors (46279488).

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

21524640 is a wasteful number, since it uses less digits than its factorization.

21524640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 44861 (or 44853 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 24.

The square root of 21524640 is about 4639.4654864542. The cubic root of 21524640 is about 278.1710728707.

The spelling of 21524640 in words is "twenty-one million, five hundred twenty-four thousand, six hundred forty".