31213210021 has 4 divisors (see below), whose sum is σ = 35672240032. Its totient is φ = 26754180012.

The previous prime is 31213209991. The next prime is 31213210037. The reversal of 31213210021 is 12001231213.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12001231213 = 1171 ⋅10248703.

It is not a de Polignac number, because 31213210021 - 2¹¹ = 31213207973 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 31213209977 and 31213210004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (31213210121) 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, 2229514995 + ... + 2229515008.

It is an arithmetic number, because the mean of its divisors is an integer number (8918060008).

Almost surely, 2^31213210021 is an apocalyptic number.

It is an amenable number.

31213210021 is a deficient number, since it is larger than the sum of its proper divisors (4459030011).

31213210021 is an equidigital number, since it uses as much as digits as its factorization.

31213210021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4459030010.

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

Adding to 31213210021 its reverse (12001231213), we get a palindrome (43214441234).

The spelling of 31213210021 in words is "thirty-one billion, two hundred thirteen million, two hundred ten thousand, twenty-one".