31123102721 has 4 divisors (see below), whose sum is σ = 31281088212. Its totient is φ = 30965117232.

The previous prime is 31123102697. The next prime is 31123102771. The reversal of 31123102721 is 12720132113.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 17255449600 + 13867653121 = 131360^2 + 117761^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31123102721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (31123102771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 78992450 + ... + 78992843.

It is an arithmetic number, because the mean of its divisors is an integer number (7820272053).

Almost surely, 2^31123102721 is an apocalyptic number.

It is an amenable number.

31123102721 is a deficient number, since it is larger than the sum of its proper divisors (157985491).

31123102721 is a wasteful number, since it uses less digits than its factorization.

31123102721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 157985490.

The product of its (nonzero) digits is 504, while the sum is 23.

Adding to 31123102721 its reverse (12720132113), we get a palindrome (43843234834).

The spelling of 31123102721 in words is "thirty-one billion, one hundred twenty-three million, one hundred two thousand, seven hundred twenty-one".