21640480 has 48 divisors (see below), whose sum is σ = 52786944. Its totient is φ = 8375040.

The previous prime is 21640477. The next prime is 21640499. The reversal of 21640480 is 8404612.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2779 + ... + 7141.

It is an arithmetic number, because the mean of its divisors is an integer number (1099728).

Almost surely, 2^21640480 is an apocalyptic number.

21640480 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21640480, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26393472).

21640480 is an abundant number, since it is smaller than the sum of its proper divisors (31146464).

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

21640480 is a wasteful number, since it uses less digits than its factorization.

21640480 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4409 (or 4401 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 25.

The square root of 21640480 is about 4651.9329315888. The cubic root of 21640480 is about 278.6691950759.

The spelling of 21640480 in words is "twenty-one million, six hundred forty thousand, four hundred eighty".