31721961 has 4 divisors (see below), whose sum is σ = 42295952. Its totient is φ = 21147972.

The previous prime is 31721953. The next prime is 31722049. The reversal of 31721961 is 16912713.

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.

It is not a de Polignac number, because 31721961 - 2³ = 31721953 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (31721941) 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, 5286991 + ... + 5286996.

It is an arithmetic number, because the mean of its divisors is an integer number (10573988).

Almost surely, 2^31721961 is an apocalyptic number.

It is an amenable number.

31721961 is a deficient number, since it is larger than the sum of its proper divisors (10573991).

31721961 is a wasteful number, since it uses less digits than its factorization.

31721961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10573990.

The product of its digits is 2268, while the sum is 30.

The square root of 31721961 is about 5632.2252263204. The cubic root of 31721961 is about 316.5580356228.

The spelling of 31721961 in words is "thirty-one million, seven hundred twenty-one thousand, nine hundred sixty-one".