25194865981 has 2 divisors, whose sum is σ = 25194865982. Its totient is φ = 25194865980.

The previous prime is 25194865933. The next prime is 25194866027. The reversal of 25194865981 is 18956849152.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 23983477956 + 1211388025 = 154866^2 + 34805^2 .

It is a cyclic number.

It is not a de Polignac number, because 25194865981 - 2⁷ = 25194865853 is a prime.

It is a super-2 number, since 2×25194865981² (a number of 22 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (25194865901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12597432990 + 12597432991.

It is an arithmetic number, because the mean of its divisors is an integer number (12597432991).

Almost surely, 2^25194865981 is an apocalyptic number.

It is an amenable number.

25194865981 is a deficient number, since it is larger than the sum of its proper divisors (1).

25194865981 is an equidigital number, since it uses as much as digits as its factorization.

25194865981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6220800, while the sum is 58.

The spelling of 25194865981 in words is "twenty-five billion, one hundred ninety-four million, eight hundred sixty-five thousand, nine hundred eighty-one".