721535690 has 16 divisors (see below), whose sum is σ = 1299191400. Its totient is φ = 288519360.

The previous prime is 721535669. The next prime is 721535713. The reversal of 721535690 is 96535127.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 674077369 + 47458321 = 25963^2 + 6889^2 .

It is a super-2 number, since 2×721535690² = 1041227503887552200, which contains 22 as substring.

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, 25736 + ... + 45884.

Almost surely, 2^721535690 is an apocalyptic number.

721535690 is a deficient number, since it is larger than the sum of its proper divisors (577655710).

721535690 is a wasteful number, since it uses less digits than its factorization.

721535690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23737.

The product of its (nonzero) digits is 56700, while the sum is 38.

The square root of 721535690 is about 26861.4163811218. The cubic root of 721535690 is about 896.9177235088.

The spelling of 721535690 in words is "seven hundred twenty-one million, five hundred thirty-five thousand, six hundred ninety".