721405656 has 64 divisors (see below), whose sum is σ = 2006143200. Its totient is φ = 240200064.

The previous prime is 721405651. The next prime is 721405721. The reversal of 721405656 is 656504127.

It is a happy number.

It is a super-2 number, since 2×721405656² = 1040852241017580672, which contains 22 as substring.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

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 721405656.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721405651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 321370 + ... + 323606.

Almost surely, 2^721405656 is an apocalyptic number.

It is an amenable number.

721405656 is an abundant number, since it is smaller than the sum of its proper divisors (1284737544).

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

721405656 is a wasteful number, since it uses less digits than its factorization.

721405656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3745 (or 3735 counting only the distinct ones).

The product of its (nonzero) digits is 50400, while the sum is 36.

The square root of 721405656 is about 26858.9958114595. The cubic root of 721405656 is about 896.8638399158.

The spelling of 721405656 in words is "seven hundred twenty-one million, four hundred five thousand, six hundred fifty-six".