21106775251 has 4 divisors (see below), whose sum is σ = 21361073832. Its totient is φ = 20852476672.

The previous prime is 21106775243. The next prime is 21106775269. The reversal of 21106775251 is 15257760112.

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

It is a cyclic number.

It is not a de Polignac number, because 21106775251 - 2³ = 21106775243 is a prime.

It is a super-2 number, since 2×21106775251² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21106775251.

It is not an unprimeable number, because it can be changed into a prime (21106775201) 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 in 3 ways as a sum of consecutive naturals, for example, 127149166 + ... + 127149331.

It is an arithmetic number, because the mean of its divisors is an integer number (5340268458).

Almost surely, 2^21106775251 is an apocalyptic number.

21106775251 is a deficient number, since it is larger than the sum of its proper divisors (254298581).

21106775251 is an equidigital number, since it uses as much as digits as its factorization.

21106775251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 254298580.

The product of its (nonzero) digits is 29400, while the sum is 37.

The spelling of 21106775251 in words is "twenty-one billion, one hundred six million, seven hundred seventy-five thousand, two hundred fifty-one".