25715171721 has 4 divisors (see below), whose sum is σ = 34286895632. Its totient is φ = 17143447812.

The previous prime is 25715171719. The next prime is 25715171731. The reversal of 25715171721 is 12717151752.

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 not a de Polignac number, because 25715171721 - 2¹ = 25715171719 is a prime.

It is a super-2 number, since 2×25715171721² (a number of 22 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 25715171721.

It is not an unprimeable number, because it can be changed into a prime (25715171701) 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, 4285861951 + ... + 4285861956.

It is an arithmetic number, because the mean of its divisors is an integer number (8571723908).

Almost surely, 2^25715171721 is an apocalyptic number.

It is an amenable number.

25715171721 is a deficient number, since it is larger than the sum of its proper divisors (8571723911).

25715171721 is an equidigital number, since it uses as much as digits as its factorization.

25715171721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8571723910.

The product of its digits is 34300, while the sum is 39.

The spelling of 25715171721 in words is "twenty-five billion, seven hundred fifteen million, one hundred seventy-one thousand, seven hundred twenty-one".