21547645249 has 4 divisors (see below), whose sum is σ = 23205156436. Its totient is φ = 19890134064.

The previous prime is 21547645213. The next prime is 21547645291. The reversal of 21547645249 is 94254674512.

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 4266702400 + 17280942849 = 65320^2 + 131457^2 .

It is a cyclic number.

It is not a de Polignac number, because 21547645249 - 2²⁵ = 21514090817 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21547645949) 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, 828755574 + ... + 828755599.

It is an arithmetic number, because the mean of its divisors is an integer number (5801289109).

Almost surely, 2^21547645249 is an apocalyptic number.

It is an amenable number.

21547645249 is a deficient number, since it is larger than the sum of its proper divisors (1657511187).

21547645249 is a wasteful number, since it uses less digits than its factorization.

21547645249 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1657511186.

The product of its digits is 2419200, while the sum is 49.

The spelling of 21547645249 in words is "twenty-one billion, five hundred forty-seven million, six hundred forty-five thousand, two hundred forty-nine".