19720656 has 30 divisors (see below), whose sum is σ = 55190850. Its totient is φ = 6573504.

The previous prime is 19720639. The next prime is 19720661. The reversal of 19720656 is 65602791.

It can be written as a sum of positive squares in only one way, i.e., 19713600 + 7056 = 4440^2 + 84^2 .

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a self number, because there is not a number n which added to its sum of digits gives 19720656.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 68331 + ... + 68618.

It is an arithmetic number, because the mean of its divisors is an integer number (1839695).

Almost surely, 2^19720656 is an apocalyptic number.

19720656 is a gapful number since it is divisible by the number (16) formed by its first and last digit.

It is an amenable number.

19720656 is an abundant number, since it is smaller than the sum of its proper divisors (35470194).

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

19720656 is a wasteful number, since it uses less digits than its factorization.

19720656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136963 (or 136954 counting only the distinct ones).

The product of its (nonzero) digits is 22680, while the sum is 36.

The square root of 19720656 is about 4440.7945235059. The cubic root of 19720656 is about 270.1720713853.

The spelling of 19720656 in words is "nineteen million, seven hundred twenty thousand, six hundred fifty-six".