21256476785 has 4 divisors (see below), whose sum is σ = 25507772148. Its totient is φ = 17005181424.

The previous prime is 21256476701. The next prime is 21256476823. The reversal of 21256476785 is 58767465212.

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

It can be written as a sum of positive squares in 2 ways, for example, as 15703097344 + 5553379441 = 125312^2 + 74521^2 .

It is a cyclic number.

It is not a de Polignac number, because 21256476785 - 2¹² = 21256472689 is a prime.

It is a super-2 number, since 2×21256476785² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2125647674 + ... + 2125647683.

It is an arithmetic number, because the mean of its divisors is an integer number (6376943037).

Almost surely, 2^21256476785 is an apocalyptic number.

It is an amenable number.

21256476785 is a deficient number, since it is larger than the sum of its proper divisors (4251295363).

21256476785 is an equidigital number, since it uses as much as digits as its factorization.

21256476785 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4251295362.

The product of its digits is 5644800, while the sum is 53.

The spelling of 21256476785 in words is "twenty-one billion, two hundred fifty-six million, four hundred seventy-six thousand, seven hundred eighty-five".