21873256991 has 2 divisors, whose sum is σ = 21873256992. Its totient is φ = 21873256990.

The previous prime is 21873256981. The next prime is 21873257017. The reversal of 21873256991 is 19965237812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21873256991 - 2⁶ = 21873256927 is a prime.

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 (21873256981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10936628495 + 10936628496.

It is an arithmetic number, because the mean of its divisors is an integer number (10936628496).

Almost surely, 2^21873256991 is an apocalyptic number.

21873256991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21873256991 is an equidigital number, since it uses as much as digits as its factorization.

21873256991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1632960, while the sum is 53.

The spelling of 21873256991 in words is "twenty-one billion, eight hundred seventy-three million, two hundred fifty-six thousand, nine hundred ninety-one".