81256251 has 16 divisors (see below), whose sum is σ = 109670400. Its totient is φ = 53510688.

The previous prime is 81256249. The next prime is 81256267. The reversal of 81256251 is 15265218.

It is not a de Polignac number, because 81256251 - 2¹ = 81256249 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81256051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 159385 + ... + 159893.

It is an arithmetic number, because the mean of its divisors is an integer number (6854400).

Almost surely, 2^81256251 is an apocalyptic number.

81256251 is a deficient number, since it is larger than the sum of its proper divisors (28414149).

81256251 is a wasteful number, since it uses less digits than its factorization.

81256251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1058.

The product of its digits is 4800, while the sum is 30.

The square root of 81256251 is about 9014.2249250837. The cubic root of 81256251 is about 433.1306597921.

The spelling of 81256251 in words is "eighty-one million, two hundred fifty-six thousand, two hundred fifty-one".