21312121031 has 4 divisors (see below), whose sum is σ = 21318765600. Its totient is φ = 21305476464.

The previous prime is 21312121021. The next prime is 21312121073. The reversal of 21312121031 is 13012121312.

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

It is a cyclic number.

It is not a de Polignac number, because 21312121031 - 2²⁶ = 21245012167 is a prime.

It is a super-2 number, since 2×21312121031² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21312121021) 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, 3317471 + ... + 3323888.

It is an arithmetic number, because the mean of its divisors is an integer number (5329691400).

Almost surely, 2^21312121031 is an apocalyptic number.

21312121031 is a deficient number, since it is larger than the sum of its proper divisors (6644569).

21312121031 is an equidigital number, since it uses as much as digits as its factorization.

21312121031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6644568.

The product of its (nonzero) digits is 72, while the sum is 17.

Adding to 21312121031 its reverse (13012121312), we get a palindrome (34324242343).

The spelling of 21312121031 in words is "twenty-one billion, three hundred twelve million, one hundred twenty-one thousand, thirty-one".