25561821 has 16 divisors (see below), whose sum is σ = 36055040. Its totient is φ = 16063920.

The previous prime is 25561817. The next prime is 25561831. The reversal of 25561821 is 12816552.

It is not a de Polignac number, because 25561821 - 2² = 25561817 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (25561831) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11706 + ... + 13716.

It is an arithmetic number, because the mean of its divisors is an integer number (2253440).

Almost surely, 2^25561821 is an apocalyptic number.

It is an amenable number.

25561821 is a deficient number, since it is larger than the sum of its proper divisors (10493219).

25561821 is a wasteful number, since it uses less digits than its factorization.

25561821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2256.

The product of its digits is 4800, while the sum is 30.

The square root of 25561821 is about 5055.8699548149. The cubic root of 25561821 is about 294.5759338307.

The spelling of 25561821 in words is "twenty-five million, five hundred sixty-one thousand, eight hundred twenty-one".