25515661 has 4 divisors (see below), whose sum is σ = 25566300. Its totient is φ = 25465024.

The previous prime is 25515619. The next prime is 25515713. The reversal of 25515661 is 16651552.

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 23097636 + 2418025 = 4806^2 + 1555^2 .

It is a cyclic number.

It is not a de Polignac number, because 25515661 - 2¹¹ = 25513613 is a prime.

It is a super-3 number, since 3×25515661³ (a number of 23 digits) contains 333 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25515361) 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, 24556 + ... + 25573.

It is an arithmetic number, because the mean of its divisors is an integer number (6391575).

Almost surely, 2^25515661 is an apocalyptic number.

It is an amenable number.

25515661 is a deficient number, since it is larger than the sum of its proper divisors (50639).

25515661 is an equidigital number, since it uses as much as digits as its factorization.

25515661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 50638.

The product of its digits is 9000, while the sum is 31.

The square root of 25515661 is about 5051.3029012325. The cubic root of 25515661 is about 294.3985101347.

The spelling of 25515661 in words is "twenty-five million, five hundred fifteen thousand, six hundred sixty-one".