725661991 has 4 divisors (see below), whose sum is σ = 726287112. Its totient is φ = 725036872.

The previous prime is 725661971. The next prime is 725661997. The reversal of 725661991 is 199166527.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 725661991 - 2²¹ = 723564839 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (725661997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 310816 + ... + 313141.

It is an arithmetic number, because the mean of its divisors is an integer number (181571778).

Almost surely, 2^725661991 is an apocalyptic number.

725661991 is a deficient number, since it is larger than the sum of its proper divisors (625121).

725661991 is a wasteful number, since it uses less digits than its factorization.

725661991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 625120.

The product of its digits is 204120, while the sum is 46.

The square root of 725661991 is about 26938.1140950884. The cubic root of 725661991 is about 898.6242317740.

The spelling of 725661991 in words is "seven hundred twenty-five million, six hundred sixty-one thousand, nine hundred ninety-one".