31113721 has 4 divisors (see below), whose sum is σ = 31623844. Its totient is φ = 30603600.

The previous prime is 31113713. The next prime is 31113749. The reversal of 31113721 is 12731113.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12731113 = 17 ⋅748889.

It can be written as a sum of positive squares in 2 ways, for example, as 7639696 + 23474025 = 2764^2 + 4845^2 .

It is a cyclic number.

It is not a de Polignac number, because 31113721 - 2³ = 31113713 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31113221) 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, 254970 + ... + 255091.

It is an arithmetic number, because the mean of its divisors is an integer number (7905961).

Almost surely, 2^31113721 is an apocalyptic number.

It is an amenable number.

31113721 is a deficient number, since it is larger than the sum of its proper divisors (510123).

31113721 is an equidigital number, since it uses as much as digits as its factorization.

31113721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 510122.

The product of its digits is 126, while the sum is 19.

The square root of 31113721 is about 5577.9674613608. The cubic root of 31113721 is about 314.5217265303.

Adding to 31113721 its reverse (12731113), we get a palindrome (43844834).

The spelling of 31113721 in words is "thirty-one million, one hundred thirteen thousand, seven hundred twenty-one".