25215781 has 2 divisors, whose sum is σ = 25215782. Its totient is φ = 25215780.

The previous prime is 25215763. The next prime is 25215821. The reversal of 25215781 is 18751252.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 24591681 + 624100 = 4959^2 + 790^2 .

It is a cyclic number.

It is not a de Polignac number, because 25215781 - 2¹⁹ = 24691493 is a prime.

It is a super-2 number, since 2×25215781² = 1271671222879922, 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 (25215731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12607890 + 12607891.

It is an arithmetic number, because the mean of its divisors is an integer number (12607891).

Almost surely, 2^25215781 is an apocalyptic number.

It is an amenable number.

25215781 is a deficient number, since it is larger than the sum of its proper divisors (1).

25215781 is an equidigital number, since it uses as much as digits as its factorization.

25215781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5600, while the sum is 31.

The square root of 25215781 is about 5021.5317384240. The cubic root of 25215781 is about 293.2406282746.

The spelling of 25215781 in words is "twenty-five million, two hundred fifteen thousand, seven hundred eighty-one".