31563661 has 4 divisors (see below), whose sum is σ = 31636000. Its totient is φ = 31491324.

The previous prime is 31563647. The next prime is 31563671. The reversal of 31563661 is 16636513.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 16636513 = 743 ⋅22391.

It is a cyclic number.

It is not a de Polignac number, because 31563661 - 2⁹ = 31563149 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 (31563601) 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, 35511 + ... + 36388.

It is an arithmetic number, because the mean of its divisors is an integer number (7909000).

Almost surely, 2^31563661 is an apocalyptic number.

It is an amenable number.

31563661 is a deficient number, since it is larger than the sum of its proper divisors (72339).

31563661 is an equidigital number, since it uses as much as digits as its factorization.

31563661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72338.

The product of its digits is 9720, while the sum is 31.

The square root of 31563661 is about 5618.1545902547. The cubic root of 31563661 is about 316.0305910939.

The spelling of 31563661 in words is "thirty-one million, five hundred sixty-three thousand, six hundred sixty-one".