31601981 has 4 divisors (see below), whose sum is σ = 31665312. Its totient is φ = 31538652.

The previous prime is 31601923. The next prime is 31601987. The reversal of 31601981 is 18910613.

It is a happy number.

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: 18910613 = 17 ⋅1112389.

It is a cyclic number.

It is not a de Polignac number, because 31601981 - 2¹⁰ = 31600957 is a prime.

It is a super-2 number, since 2×31601981² = 1997370406248722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31601987) 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, 30911 + ... + 31916.

It is an arithmetic number, because the mean of its divisors is an integer number (7916328).

Almost surely, 2^31601981 is an apocalyptic number.

It is an amenable number.

31601981 is a deficient number, since it is larger than the sum of its proper divisors (63331).

31601981 is an equidigital number, since it uses as much as digits as its factorization.

31601981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63330.

The product of its (nonzero) digits is 1296, while the sum is 29.

The square root of 31601981 is about 5621.5639283032. The cubic root of 31601981 is about 316.1584321440.

The spelling of 31601981 in words is "thirty-one million, six hundred one thousand, nine hundred eighty-one".