21012042991 has 2 divisors, whose sum is σ = 21012042992. Its totient is φ = 21012042990.

The previous prime is 21012042967. The next prime is 21012043021. The reversal of 21012042991 is 19924021012.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21012042991 - 2⁹ = 21012042479 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21012042911) 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, 10506021495 + 10506021496.

It is an arithmetic number, because the mean of its divisors is an integer number (10506021496).

Almost surely, 2^21012042991 is an apocalyptic number.

21012042991 is a deficient number, since it is larger than the sum of its proper divisors (1).

21012042991 is an equidigital number, since it uses as much as digits as its factorization.

21012042991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2592, while the sum is 31.

The spelling of 21012042991 in words is "twenty-one billion, twelve million, forty-two thousand, nine hundred ninety-one".