81000257 has 8 divisors (see below), whose sum is σ = 92362536. Its totient is φ = 70371072.

The previous prime is 81000233. The next prime is 81000263. The reversal of 81000257 is 75200018.

It can be written as a sum of positive squares in 4 ways, for example, as 790321 + 80209936 = 889^2 + 8956^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81000257 - 2⁸ = 81000001 is a prime.

It is a super-2 number, since 2×81000257² = 13122083268132098, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81000757) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 183038 + ... + 183479.

It is an arithmetic number, because the mean of its divisors is an integer number (11545317).

Almost surely, 2^81000257 is an apocalyptic number.

It is an amenable number.

81000257 is a deficient number, since it is larger than the sum of its proper divisors (11362279).

81000257 is a wasteful number, since it uses less digits than its factorization.

81000257 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 366547.

The product of its (nonzero) digits is 560, while the sum is 23.

The square root of 81000257 is about 9000.0142777665. The cubic root of 81000257 is about 432.6753286944.

The spelling of 81000257 in words is "eighty-one million, two hundred fifty-seven", and thus it is an aban number.