20645720 has 32 divisors (see below), whose sum is σ = 48474720. Its totient is φ = 7898880.

The previous prime is 20645711. The next prime is 20645749. The reversal of 20645720 is 2754602.

It is a self number, because there is not a number n which added to its sum of digits gives 20645720.

It is a congruent number.

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, 10301 + ... + 12140.

It is an arithmetic number, because the mean of its divisors is an integer number (1514835).

Almost surely, 2^20645720 is an apocalyptic number.

20645720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

20645720 is an abundant number, since it is smaller than the sum of its proper divisors (27829000).

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

20645720 is a wasteful number, since it uses less digits than its factorization.

20645720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22475 (or 22471 counting only the distinct ones).

The product of its (nonzero) digits is 3360, while the sum is 26.

The square root of 20645720 is about 4543.7561554291. The cubic root of 20645720 is about 274.3321313847.

The spelling of 20645720 in words is "twenty million, six hundred forty-five thousand, seven hundred twenty".