21161215231 has 4 divisors (see below), whose sum is σ = 22789001032. Its totient is φ = 19533429432.

The previous prime is 21161215223. The next prime is 21161215247. The reversal of 21161215231 is 13251216112.

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 21161215231 - 2³ = 21161215223 is a prime.

It is a super-2 number, since 2×21161215231² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21161215196 and 21161215205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21161215261) 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, 813892881 + ... + 813892906.

It is an arithmetic number, because the mean of its divisors is an integer number (5697250258).

Almost surely, 2^21161215231 is an apocalyptic number.

21161215231 is a deficient number, since it is larger than the sum of its proper divisors (1627785801).

21161215231 is a wasteful number, since it uses less digits than its factorization.

21161215231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1627785800.

The product of its digits is 720, while the sum is 25.

The spelling of 21161215231 in words is "twenty-one billion, one hundred sixty-one million, two hundred fifteen thousand, two hundred thirty-one".