31111921 has 4 divisors (see below), whose sum is σ = 32942052. Its totient is φ = 29281792.

The previous prime is 31111903. The next prime is 31111937. The reversal of 31111921 is 12911113.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12911113 = 37 ⋅348949.

It can be written as a sum of positive squares in 2 ways, for example, as 28740321 + 2371600 = 5361^2 + 1540^2 .

It is a cyclic number.

It is not a de Polignac number, because 31111921 - 2¹⁹ = 30587633 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31111961) 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, 915040 + ... + 915073.

It is an arithmetic number, because the mean of its divisors is an integer number (8235513).

Almost surely, 2^31111921 is an apocalyptic number.

It is an amenable number.

31111921 is a deficient number, since it is larger than the sum of its proper divisors (1830131).

31111921 is a wasteful number, since it uses less digits than its factorization.

31111921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1830130.

The product of its digits is 54, while the sum is 19.

The square root of 31111921 is about 5577.8061099325. The cubic root of 31111921 is about 314.5156611459.

The spelling of 31111921 in words is "thirty-one million, one hundred eleven thousand, nine hundred twenty-one".