21128991679 has 2 divisors, whose sum is σ = 21128991680. Its totient is φ = 21128991678.

The previous prime is 21128991661. The next prime is 21128991683. The reversal of 21128991679 is 97619982112.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21128991679 - 2⁷ = 21128991551 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21128991649) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10564495839 + 10564495840.

It is an arithmetic number, because the mean of its divisors is an integer number (10564495840).

Almost surely, 2^21128991679 is an apocalyptic number.

21128991679 is a deficient number, since it is larger than the sum of its proper divisors (1).

21128991679 is an equidigital number, since it uses as much as digits as its factorization.

21128991679 is an evil number, because the sum of its binary digits is even.

The product of its digits is 979776, while the sum is 55.

The spelling of 21128991679 in words is "twenty-one billion, one hundred twenty-eight million, nine hundred ninety-one thousand, six hundred seventy-nine".