21123131221999 has 2 divisors, whose sum is σ = 21123131222000. Its totient is φ = 21123131221998.

The previous prime is 21123131221991. The next prime is 21123131222003. The reversal of 21123131221999 is 99912213132112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21123131221999 - 2³ = 21123131221991 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21123131221991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10561565610999 + 10561565611000.

It is an arithmetic number, because the mean of its divisors is an integer number (10561565611000).

Almost surely, 2^{21123131221999} is an apocalyptic number.

21123131221999 is a deficient number, since it is larger than the sum of its proper divisors (1).

21123131221999 is an equidigital number, since it uses as much as digits as its factorization.

21123131221999 is an evil number, because the sum of its binary digits is even.

The product of its digits is 104976, while the sum is 46.

The spelling of 21123131221999 in words is "twenty-one trillion, one hundred twenty-three billion, one hundred thirty-one million, two hundred twenty-one thousand, nine hundred ninety-nine".