21273967021 has 2 divisors, whose sum is σ = 21273967022. Its totient is φ = 21273967020.

The previous prime is 21273966983. The next prime is 21273967051. The reversal of 21273967021 is 12076937212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17454108996 + 3819858025 = 132114^2 + 61805^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21273967021 is a prime.

It is a super-2 number, since 2×21273967021² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21273967051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10636983510 + 10636983511.

It is an arithmetic number, because the mean of its divisors is an integer number (10636983511).

Almost surely, 2^21273967021 is an apocalyptic number.

It is an amenable number.

21273967021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21273967021 is an equidigital number, since it uses as much as digits as its factorization.

21273967021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 63504, while the sum is 40.

The spelling of 21273967021 in words is "twenty-one billion, two hundred seventy-three million, nine hundred sixty-seven thousand, twenty-one".