21138878867 has 2 divisors, whose sum is σ = 21138878868. Its totient is φ = 21138878866.

The previous prime is 21138878807. The next prime is 21138878903. The reversal of 21138878867 is 76887883112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21138878867 - 2⁸ = 21138878611 is a prime.

It is not a weakly prime, because it can be changed into another prime (21138878807) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10569439433 + 10569439434.

It is an arithmetic number, because the mean of its divisors is an integer number (10569439434).

Almost surely, 2^21138878867 is an apocalyptic number.

21138878867 is a deficient number, since it is larger than the sum of its proper divisors (1).

21138878867 is an equidigital number, since it uses as much as digits as its factorization.

21138878867 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7225344, while the sum is 59.

The spelling of 21138878867 in words is "twenty-one billion, one hundred thirty-eight million, eight hundred seventy-eight thousand, eight hundred sixty-seven".