25378391821 has 2 divisors, whose sum is σ = 25378391822. Its totient is φ = 25378391820.

The previous prime is 25378391803. The next prime is 25378391833. The reversal of 25378391821 is 12819387352.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17022420900 + 8355970921 = 130470^2 + 91411^2 .

It is a cyclic number.

It is not a de Polignac number, because 25378391821 - 2²⁷ = 25244174093 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (25378391851) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12689195910 + 12689195911.

It is an arithmetic number, because the mean of its divisors is an integer number (12689195911).

Almost surely, 2^25378391821 is an apocalyptic number.

It is an amenable number.

25378391821 is a deficient number, since it is larger than the sum of its proper divisors (1).

25378391821 is an equidigital number, since it uses as much as digits as its factorization.

25378391821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 725760, while the sum is 49.

The spelling of 25378391821 in words is "twenty-five billion, three hundred seventy-eight million, three hundred ninety-one thousand, eight hundred twenty-one".