21736725817 has 4 divisors (see below), whose sum is σ = 21737437840. Its totient is φ = 21736013796.

The previous prime is 21736725761. The next prime is 21736725833. The reversal of 21736725817 is 71852763712.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21736725817 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21736725887) 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, 308067 + ... + 371992.

It is an arithmetic number, because the mean of its divisors is an integer number (5434359460).

Almost surely, 2^21736725817 is an apocalyptic number.

It is an amenable number.

21736725817 is a deficient number, since it is larger than the sum of its proper divisors (712023).

21736725817 is an equidigital number, since it uses as much as digits as its factorization.

21736725817 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 712022.

The product of its digits is 987840, while the sum is 49.

The spelling of 21736725817 in words is "twenty-one billion, seven hundred thirty-six million, seven hundred twenty-five thousand, eight hundred seventeen".