666891731 has 16 divisors (see below), whose sum is σ = 741581568. Its totient is φ = 594660000.

The previous prime is 666891707. The next prime is 666891749. The reversal of 666891731 is 137198666.

It is a happy number.

It is not a de Polignac number, because 666891731 - 2²⁶ = 599782867 is a prime.

It is a super-2 number, since 2×666891731² = 889489161752352722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (666861731) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 118481 + ... + 123981.

It is an arithmetic number, because the mean of its divisors is an integer number (46348848).

Almost surely, 2^666891731 is an apocalyptic number.

666891731 is a deficient number, since it is larger than the sum of its proper divisors (74689837).

666891731 is a wasteful number, since it uses less digits than its factorization.

666891731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5722.

The product of its digits is 326592, while the sum is 47.

The square root of 666891731 is about 25824.2469590112. The cubic root of 666891731 is about 873.6787595783.

The spelling of 666891731 in words is "six hundred sixty-six million, eight hundred ninety-one thousand, seven hundred thirty-one".