25781999 has 2 divisors, whose sum is σ = 25782000. Its totient is φ = 25781998.

The previous prime is 25781963. The next prime is 25782019. The reversal of 25781999 is 99918752.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 25781999 - 2¹² = 25777903 is a prime.

It is a super-2 number, since 2×25781999² = 1329422944872002, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (25781909) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12890999 + 12891000.

It is an arithmetic number, because the mean of its divisors is an integer number (12891000).

Almost surely, 2^25781999 is an apocalyptic number.

25781999 is a deficient number, since it is larger than the sum of its proper divisors (1).

25781999 is an equidigital number, since it uses as much as digits as its factorization.

25781999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 408240, while the sum is 50.

The square root of 25781999 is about 5077.5977587832. The cubic root of 25781999 is about 295.4192984139.

The spelling of 25781999 in words is "twenty-five million, seven hundred eighty-one thousand, nine hundred ninety-nine".