21312120031 has 2 divisors, whose sum is σ = 21312120032. Its totient is φ = 21312120030.

The previous prime is 21312120029. The next prime is 21312120043. The reversal of 21312120031 is 13002121312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21312120031 - 2¹ = 21312120029 is a prime.

It is a super-2 number, since 2×21312120031² (a number of 21 digits) contains 22 as substring.

Together with 21312120029, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 21312119987 and 21312120014.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21312129031) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10656060015 + 10656060016.

It is an arithmetic number, because the mean of its divisors is an integer number (10656060016).

Almost surely, 2^21312120031 is an apocalyptic number.

21312120031 is a deficient number, since it is larger than the sum of its proper divisors (1).

21312120031 is an equidigital number, since it uses as much as digits as its factorization.

21312120031 is an evil number, because the sum of its binary digits is even.

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

Adding to 21312120031 its reverse (13002121312), we get a palindrome (34314241343).

The spelling of 21312120031 in words is "twenty-one billion, three hundred twelve million, one hundred twenty thousand, thirty-one".