21363712921 has 2 divisors, whose sum is σ = 21363712922. Its totient is φ = 21363712920.

The previous prime is 21363712831. The next prime is 21363712943. The reversal of 21363712921 is 12921736312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16845184521 + 4518528400 = 129789^2 + 67220^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21363712921 is a prime.

It is not a weakly prime, because it can be changed into another prime (21363715921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10681856460 + 10681856461.

It is an arithmetic number, because the mean of its divisors is an integer number (10681856461).

Almost surely, 2^21363712921 is an apocalyptic number.

It is an amenable number.

21363712921 is a deficient number, since it is larger than the sum of its proper divisors (1).

21363712921 is an equidigital number, since it uses as much as digits as its factorization.

21363712921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 27216, while the sum is 37.

The spelling of 21363712921 in words is "twenty-one billion, three hundred sixty-three million, seven hundred twelve thousand, nine hundred twenty-one".