21002131231 has 4 divisors (see below), whose sum is σ = 21398397912. Its totient is φ = 20605864552.

The previous prime is 21002131229. The next prime is 21002131291. The reversal of 21002131231 is 13213120012.

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 21002131231 - 2¹ = 21002131229 is a prime.

It is a super-3 number, since 3×21002131231³ (a number of 32 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002131201) 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, 198133261 + ... + 198133366.

It is an arithmetic number, because the mean of its divisors is an integer number (5349599478).

Almost surely, 2^21002131231 is an apocalyptic number.

21002131231 is a deficient number, since it is larger than the sum of its proper divisors (396266681).

21002131231 is an equidigital number, since it uses as much as digits as its factorization.

21002131231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 396266680.

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

Adding to 21002131231 its reverse (13213120012), we get a palindrome (34215251243).

The spelling of 21002131231 in words is "twenty-one billion, two million, one hundred thirty-one thousand, two hundred thirty-one".