21547142257 has 4 divisors (see below), whose sum is σ = 21691754100. Its totient is φ = 21402530416.

The previous prime is 21547142237. The next prime is 21547142263. The reversal of 21547142257 is 75224174512.

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 754655841 + 20792486416 = 27471^2 + 144196^2 .

It is a cyclic number.

It is not a de Polignac number, because 21547142257 - 2¹⁵ = 21547109489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21547142207) 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, 72305698 + ... + 72305995.

It is an arithmetic number, because the mean of its divisors is an integer number (5422938525).

Almost surely, 2^21547142257 is an apocalyptic number.

It is an amenable number.

21547142257 is a deficient number, since it is larger than the sum of its proper divisors (144611843).

21547142257 is a wasteful number, since it uses less digits than its factorization.

21547142257 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 144611842.

The product of its digits is 156800, while the sum is 40.

The spelling of 21547142257 in words is "twenty-one billion, five hundred forty-seven million, one hundred forty-two thousand, two hundred fifty-seven".