31123012021 has 4 divisors (see below), whose sum is σ = 32953777452. Its totient is φ = 29292246592.

The previous prime is 31123011991. The next prime is 31123012031. The reversal of 31123012021 is 12021032113.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12021032113 = 59 ⋅203746307.

It can be written as a sum of positive squares in 2 ways, for example, as 14547736996 + 16575275025 = 120614^2 + 128745^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-31123012021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 31123011986 and 31123012004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31123012031) 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, 915382690 + ... + 915382723.

It is an arithmetic number, because the mean of its divisors is an integer number (8238444363).

Almost surely, 2^31123012021 is an apocalyptic number.

It is an amenable number.

31123012021 is a deficient number, since it is larger than the sum of its proper divisors (1830765431).

31123012021 is a wasteful number, since it uses less digits than its factorization.

31123012021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1830765430.

The product of its (nonzero) digits is 72, while the sum is 16.

Adding to 31123012021 its reverse (12021032113), we get a palindrome (43144044134).

The spelling of 31123012021 in words is "thirty-one billion, one hundred twenty-three million, twelve thousand, twenty-one".