25397535721 has 2 divisors, whose sum is σ = 25397535722. Its totient is φ = 25397535720.

The previous prime is 25397535677. The next prime is 25397535763. The reversal of 25397535721 is 12753579352.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 23154187225 + 2243348496 = 152165^2 + 47364^2 .

It is a cyclic number.

It is not a de Polignac number, because 25397535721 - 2⁹ = 25397535209 is a prime.

It is not a weakly prime, because it can be changed into another prime (25397535221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12698767860 + 12698767861.

It is an arithmetic number, because the mean of its divisors is an integer number (12698767861).

Almost surely, 2^25397535721 is an apocalyptic number.

It is an amenable number.

25397535721 is a deficient number, since it is larger than the sum of its proper divisors (1).

25397535721 is an equidigital number, since it uses as much as digits as its factorization.

25397535721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1984500, while the sum is 49.

The spelling of 25397535721 in words is "twenty-five billion, three hundred ninety-seven million, five hundred thirty-five thousand, seven hundred twenty-one".