25515122221 has 4 divisors (see below), whose sum is σ = 25667907552. Its totient is φ = 25362336892.

The previous prime is 25515122207. The next prime is 25515122233. The reversal of 25515122221 is 12222151552.

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 not a de Polignac number, because 25515122221 - 2²³ = 25506733613 is a prime.

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 25515122221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25515122251) 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, 76392415 + ... + 76392748.

It is an arithmetic number, because the mean of its divisors is an integer number (6416976888).

Almost surely, 2^25515122221 is an apocalyptic number.

It is an amenable number.

25515122221 is a deficient number, since it is larger than the sum of its proper divisors (152785331).

25515122221 is a wasteful number, since it uses less digits than its factorization.

25515122221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 152785330.

The product of its digits is 4000, while the sum is 28.

Adding to 25515122221 its reverse (12222151552), we get a palindrome (37737273773).

The spelling of 25515122221 in words is "twenty-five billion, five hundred fifteen million, one hundred twenty-two thousand, two hundred twenty-one".