721739556 has 72 divisors (see below), whose sum is σ = 1963483704. Its totient is φ = 222704640.

The previous prime is 721739533. The next prime is 721739561. The reversal of 721739556 is 655937127.

721739556 is a `hidden beast` number, since 7 + 21 + 73 + 9 + 556 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 171086400 + 550653156 = 13080^2 + 23466^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 27666 + ... + 46998.

It is an arithmetic number, because the mean of its divisors is an integer number (27270607).

Almost surely, 2^721739556 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 721739556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (981741852).

721739556 is an abundant number, since it is smaller than the sum of its proper divisors (1241744148).

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

721739556 is a wasteful number, since it uses less digits than its factorization.

721739556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19421 (or 19416 counting only the distinct ones).

The product of its digits is 396900, while the sum is 45.

The square root of 721739556 is about 26865.2108869445. The cubic root of 721739556 is about 897.0021886354.

The spelling of 721739556 in words is "seven hundred twenty-one million, seven hundred thirty-nine thousand, five hundred fifty-six".