25821781 has 2 divisors, whose sum is σ = 25821782. Its totient is φ = 25821780.

The previous prime is 25821749. The next prime is 25821787. The reversal of 25821781 is 18712852.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14699556 + 11122225 = 3834^2 + 3335^2 .

It is a cyclic number.

It is not a de Polignac number, because 25821781 - 2⁵ = 25821749 is a prime.

It is a super-2 number, since 2×25821781² = 1333528748023922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (25821787) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 12910890 + 12910891.

It is an arithmetic number, because the mean of its divisors is an integer number (12910891).

Almost surely, 2^25821781 is an apocalyptic number.

It is an amenable number.

25821781 is a deficient number, since it is larger than the sum of its proper divisors (1).

25821781 is an equidigital number, since it uses as much as digits as its factorization.

25821781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8960, while the sum is 34.

The square root of 25821781 is about 5081.5136524465. The cubic root of 25821781 is about 295.5711657563.

The spelling of 25821781 in words is "twenty-five million, eight hundred twenty-one thousand, seven hundred eighty-one".