721721864 has 8 divisors (see below), whose sum is σ = 1353228510. Its totient is φ = 360860928.

The previous prime is 721721863. The next prime is 721721909. The reversal of 721721864 is 468127127.

It can be written as a sum of positive squares in only one way, i.e., 476548900 + 245172964 = 21830^2 + 15658^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (721721863) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 45107609 + ... + 45107624.

Almost surely, 2^721721864 is an apocalyptic number.

It is an amenable number.

721721864 is a deficient number, since it is larger than the sum of its proper divisors (631506646).

721721864 is a wasteful number, since it uses less digits than its factorization.

721721864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 90215239 (or 90215235 counting only the distinct ones).

The product of its digits is 37632, while the sum is 38.

The square root of 721721864 is about 26864.8816115017. The cubic root of 721721864 is about 896.9948591713.

The spelling of 721721864 in words is "seven hundred twenty-one million, seven hundred twenty-one thousand, eight hundred sixty-four".