21156428099 has 4 divisors (see below), whose sum is σ = 21156869736. Its totient is φ = 21155986464.

The previous prime is 21156428071. The next prime is 21156428101. The reversal of 21156428099 is 99082465112.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21156428099 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21156424099) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 138809 + ... + 248154.

It is an arithmetic number, because the mean of its divisors is an integer number (5289217434).

Almost surely, 2^21156428099 is an apocalyptic number.

21156428099 is a deficient number, since it is larger than the sum of its proper divisors (441637).

21156428099 is an equidigital number, since it uses as much as digits as its factorization.

21156428099 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 441636.

The product of its (nonzero) digits is 311040, while the sum is 47.

The spelling of 21156428099 in words is "twenty-one billion, one hundred fifty-six million, four hundred twenty-eight thousand, ninety-nine".