20640408 has 32 divisors (see below), whose sum is σ = 51716400. Its totient is φ = 6864768.

The previous prime is 20640401. The next prime is 20640437. The reversal of 20640408 is 80404602.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20640401) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16410 + ... + 17622.

Almost surely, 2^20640408 is an apocalyptic number.

It is an amenable number.

20640408 is an abundant number, since it is smaller than the sum of its proper divisors (31075992).

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

20640408 is a wasteful number, since it uses less digits than its factorization.

20640408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1931 (or 1927 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 24.

The square root of 20640408 is about 4543.1715794145. The cubic root of 20640408 is about 274.3086014508.

The spelling of 20640408 in words is "twenty million, six hundred forty thousand, four hundred eight".