21212231531 has 2 divisors, whose sum is σ = 21212231532. Its totient is φ = 21212231530.

The previous prime is 21212231483. The next prime is 21212231549. The reversal of 21212231531 is 13513221212.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21212231531 is a prime.

It is a super-2 number, since 2×21212231531² (a number of 21 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21212231497 and 21212231506.

It is not a weakly prime, because it can be changed into another prime (21212231581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606115765 + 10606115766.

It is an arithmetic number, because the mean of its divisors is an integer number (10606115766).

Almost surely, 2^21212231531 is an apocalyptic number.

21212231531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21212231531 is an equidigital number, since it uses as much as digits as its factorization.

21212231531 is an evil number, because the sum of its binary digits is even.

The product of its digits is 720, while the sum is 23.

Adding to 21212231531 its reverse (13513221212), we get a palindrome (34725452743).

The spelling of 21212231531 in words is "twenty-one billion, two hundred twelve million, two hundred thirty-one thousand, five hundred thirty-one".