20640680 has 16 divisors (see below), whose sum is σ = 46441620. Its totient is φ = 8256256.

The previous prime is 20640679. The next prime is 20640713. The reversal of 20640680 is 8604602.

It can be written as a sum of positive squares in 2 ways, for example, as 19166884 + 1473796 = 4378^2 + 1214^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 257969 + ... + 258048.

Almost surely, 2^20640680 is an apocalyptic number.

20640680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20640680 is an abundant number, since it is smaller than the sum of its proper divisors (25800940).

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

20640680 is a wasteful number, since it uses less digits than its factorization.

20640680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 516028 (or 516024 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 26.

The square root of 20640680 is about 4543.2015143509. The cubic root of 20640680 is about 274.3098063949.

The spelling of 20640680 in words is "twenty million, six hundred forty thousand, six hundred eighty".