721671657 has 32 divisors (see below), whose sum is σ = 1141248000. Its totient is φ = 405360144.

The previous prime is 721671653. The next prime is 721671659. The reversal of 721671657 is 756176127.

It is not a de Polignac number, because 721671657 - 2² = 721671653 is a prime.

It is not an unprimeable number, because it can be changed into a prime (721671653) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 54768 + ... + 66654.

It is an arithmetic number, because the mean of its divisors is an integer number (35664000).

Almost surely, 2^721671657 is an apocalyptic number.

It is an amenable number.

721671657 is a deficient number, since it is larger than the sum of its proper divisors (419576343).

721671657 is a wasteful number, since it uses less digits than its factorization.

721671657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11970 (or 11956 counting only the distinct ones).

The product of its digits is 123480, while the sum is 42.

The square root of 721671657 is about 26863.9471597158. The cubic root of 721671657 is about 896.9740586998.

The spelling of 721671657 in words is "seven hundred twenty-one million, six hundred seventy-one thousand, six hundred fifty-seven".