20685640 has 32 divisors (see below), whose sum is σ = 47537280. Its totient is φ = 8097472.

The previous prime is 20685631. The next prime is 20685653. The reversal of 20685640 is 4658602.

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, 3622 + ... + 7381.

It is an arithmetic number, because the mean of its divisors is an integer number (1485540).

Almost surely, 2^20685640 is an apocalyptic number.

20685640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20685640 is an abundant number, since it is smaller than the sum of its proper divisors (26851640).

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

20685640 is a wasteful number, since it uses less digits than its factorization.

20685640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11061 (or 11057 counting only the distinct ones).

The product of its (nonzero) digits is 11520, while the sum is 31.

The square root of 20685640 is about 4548.1468753768. The cubic root of 20685640 is about 274.5088312504.

The spelling of 20685640 in words is "twenty million, six hundred eighty-five thousand, six hundred forty".