21020012231 has 2 divisors, whose sum is σ = 21020012232. Its totient is φ = 21020012230.

The previous prime is 21020012207. The next prime is 21020012323. The reversal of 21020012231 is 13221002012.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21020012231 is a prime.

It is a super-2 number, since 2×21020012231² (a number of 21 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21020014231) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510006115 + 10510006116.

It is an arithmetic number, because the mean of its divisors is an integer number (10510006116).

Almost surely, 2^21020012231 is an apocalyptic number.

21020012231 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020012231 is an equidigital number, since it uses as much as digits as its factorization.

21020012231 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48, while the sum is 14.

Adding to 21020012231 its reverse (13221002012), we get a palindrome (34241014243).

The spelling of 21020012231 in words is "twenty-one billion, twenty million, twelve thousand, two hundred thirty-one".