21213617231 has 4 divisors (see below), whose sum is σ = 21213912552. Its totient is φ = 21213321912.

The previous prime is 21213617219. The next prime is 21213617239. The reversal of 21213617231 is 13271631212.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21213617231 - 2²⁶ = 21146508367 is a prime.

It is a super-2 number, since 2×21213617231² (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 = 21213617194 and 21213617203.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21213617239) 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, 37400 + ... + 209346.

It is an arithmetic number, because the mean of its divisors is an integer number (5303478138).

Almost surely, 2^21213617231 is an apocalyptic number.

21213617231 is a deficient number, since it is larger than the sum of its proper divisors (295321).

21213617231 is a wasteful number, since it uses less digits than its factorization.

21213617231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 295320.

The product of its digits is 3024, while the sum is 29.

The spelling of 21213617231 in words is "twenty-one billion, two hundred thirteen million, six hundred seventeen thousand, two hundred thirty-one".