20516640 has 48 divisors (see below), whose sum is σ = 64628928. Its totient is φ = 5470976.

The previous prime is 20516609. The next prime is 20516681. The reversal of 20516640 is 4661502.

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 20516640.

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, 20892 + ... + 21851.

It is an arithmetic number, because the mean of its divisors is an integer number (1346436).

Almost surely, 2^20516640 is an apocalyptic number.

20516640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20516640 is an abundant number, since it is smaller than the sum of its proper divisors (44112288).

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

20516640 is a wasteful number, since it uses less digits than its factorization.

20516640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42761 (or 42753 counting only the distinct ones).

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 20516640 is about 4529.5297769195. The cubic root of 20516640 is about 273.7592144685.

The spelling of 20516640 in words is "twenty million, five hundred sixteen thousand, six hundred forty".