25661921 has 8 divisors (see below), whose sum is σ = 25935624. Its totient is φ = 25390080.

The previous prime is 25661869. The next prime is 25661929. The reversal of 25661921 is 12916652.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 7480225 + 18181696 = 2735^2 + 4264^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-25661921 is a prime.

It is a super-3 number, since 3×25661921³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (25661929) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 55925 + ... + 56381.

It is an arithmetic number, because the mean of its divisors is an integer number (3241953).

Almost surely, 2^25661921 is an apocalyptic number.

It is an amenable number.

25661921 is a deficient number, since it is larger than the sum of its proper divisors (273703).

25661921 is a wasteful number, since it uses less digits than its factorization.

25661921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 931.

The product of its digits is 6480, while the sum is 32.

The square root of 25661921 is about 5065.7596666245. The cubic root of 25661921 is about 294.9599524301.

The spelling of 25661921 in words is "twenty-five million, six hundred sixty-one thousand, nine hundred twenty-one".