25218392809 has 3 divisors (see below), whose sum is σ = 25218551613. Its totient is φ = 25218234006.

The previous prime is 25218392783. The next prime is 25218392819. The reversal of 25218392809 is 90829381252.

The square root of 25218392809 is 158803.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is not a de Polignac number, because 25218392809 - 2⁵ = 25218392777 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (25218392819) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 79402 + ... + 238204.

It is an arithmetic number, because the mean of its divisors is an integer number (8406183871).

Almost surely, 2^25218392809 is an apocalyptic number.

25218392809 is the 158803-rd square number.

25218392809 is the 79402-nd centered octagonal number.

It is an amenable number.

25218392809 is a deficient number, since it is larger than the sum of its proper divisors (158804).

25218392809 is an frugal number, since it uses more digits than its factorization.

25218392809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 317606 (or 158803 counting only the distinct ones).

The product of its (nonzero) digits is 622080, while the sum is 49.

Multiplying 25218392809 by its sum of digits (49), we get a square (1235701247641 = 1111621²).

The spelling of 25218392809 in words is "twenty-five billion, two hundred eighteen million, three hundred ninety-two thousand, eight hundred nine".