31291921 has 8 divisors (see below), whose sum is σ = 31716288. Its totient is φ = 30870000.

The previous prime is 31291903. The next prime is 31291943. The reversal of 31291921 is 12919213.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 31291921 - 2⁹ = 31291409 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 31291921.

It is not an unprimeable number, because it can be changed into a prime (31291991) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 49276 + ... + 49906.

It is an arithmetic number, because the mean of its divisors is an integer number (3964536).

Almost surely, 2^31291921 is an apocalyptic number.

It is an amenable number.

31291921 is a deficient number, since it is larger than the sum of its proper divisors (424367).

31291921 is a wasteful number, since it uses less digits than its factorization.

31291921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1223.

The product of its digits is 972, while the sum is 28.

The square root of 31291921 is about 5593.9182153478. The cubic root of 31291921 is about 315.1210452746.

It can be divided in two parts, 3129 and 1921, that added together give a triangular number (5050 = T₁₀₀).

The spelling of 31291921 in words is "thirty-one million, two hundred ninety-one thousand, nine hundred twenty-one".