31387661 has 4 divisors (see below), whose sum is σ = 33234012. Its totient is φ = 29541312.

The previous prime is 31387649. The next prime is 31387679. The reversal of 31387661 is 16678313.

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

It can be written as a sum of positive squares in 2 ways, for example, as 26574025 + 4813636 = 5155^2 + 2194^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31387661 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 (31387621) 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, 923150 + ... + 923183.

It is an arithmetic number, because the mean of its divisors is an integer number (8308503).

Almost surely, 2^31387661 is an apocalyptic number.

It is an amenable number.

31387661 is a deficient number, since it is larger than the sum of its proper divisors (1846351).

31387661 is a wasteful number, since it uses less digits than its factorization.

31387661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1846350.

The product of its digits is 18144, while the sum is 35.

The square root of 31387661 is about 5602.4691877778. The cubic root of 31387661 is about 315.4420969635.

The spelling of 31387661 in words is "thirty-one million, three hundred eighty-seven thousand, six hundred sixty-one".