21129749791 has 16 divisors (see below), whose sum is σ = 21964128480. Its totient is φ = 20312174080.

The previous prime is 21129749783. The next prime is 21129749807. The reversal of 21129749791 is 19794792112.

It is a happy number.

It is not a de Polignac number, because 21129749791 - 2³ = 21129749783 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21129749741) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1059276 + ... + 1079038.

It is an arithmetic number, because the mean of its divisors is an integer number (1372758030).

Almost surely, 2^21129749791 is an apocalyptic number.

21129749791 is a deficient number, since it is larger than the sum of its proper divisors (834378689).

21129749791 is a wasteful number, since it uses less digits than its factorization.

21129749791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20186.

The product of its digits is 571536, while the sum is 52.

The spelling of 21129749791 in words is "twenty-one billion, one hundred twenty-nine million, seven hundred forty-nine thousand, seven hundred ninety-one".