25506781 has 2 divisors, whose sum is σ = 25506782. Its totient is φ = 25506780.

The previous prime is 25506779. The next prime is 25506823. The reversal of 25506781 is 18760552.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 25452025 + 54756 = 5045^2 + 234^2 .

It is a cyclic number.

It is not a de Polignac number, because 25506781 - 2¹ = 25506779 is a prime.

It is a super-2 number, since 2×25506781² = 1301191753963922, which contains 22 as substring.

Together with 25506779, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (25506751) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12753390 + 12753391.

It is an arithmetic number, because the mean of its divisors is an integer number (12753391).

Almost surely, 2^25506781 is an apocalyptic number.

It is an amenable number.

25506781 is a deficient number, since it is larger than the sum of its proper divisors (1).

25506781 is an equidigital number, since it uses as much as digits as its factorization.

25506781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 16800, while the sum is 34.

The square root of 25506781 is about 5050.4238435997. The cubic root of 25506781 is about 294.3643538296.

The spelling of 25506781 in words is "twenty-five million, five hundred six thousand, seven hundred eighty-one".