21105562051 has 4 divisors (see below), whose sum is σ = 24120642352. Its totient is φ = 18090481752.

The previous prime is 21105562043. The next prime is 21105562117. The reversal of 21105562051 is 15026550112.

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

It is not a de Polignac number, because 21105562051 - 2³ = 21105562043 is a prime.

It is a super-2 number, since 2×21105562051² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21105562651) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1507540140 + ... + 1507540153.

It is an arithmetic number, because the mean of its divisors is an integer number (6030160588).

Almost surely, 2^21105562051 is an apocalyptic number.

21105562051 is a deficient number, since it is larger than the sum of its proper divisors (3015080301).

21105562051 is an equidigital number, since it uses as much as digits as its factorization.

21105562051 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3015080300.

The product of its (nonzero) digits is 3000, while the sum is 28.

The spelling of 21105562051 in words is "twenty-one billion, one hundred five million, five hundred sixty-two thousand, fifty-one".