81581151 has 16 divisors (see below), whose sum is σ = 111339360. Its totient is φ = 53114880.

The previous prime is 81581131. The next prime is 81581173. The reversal of 81581151 is 15118518.

81581151 is a nontrivial binomial coefficient, being equal to C(12774, 2).

It is a de Polignac number, because none of the positive numbers 2^k-81581151 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81581111) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 37255 + ... + 39383.

It is an arithmetic number, because the mean of its divisors is an integer number (6958710).

Almost surely, 2^81581151 is an apocalyptic number.

81581151 is the 12773-rd triangular number and also the 6387-th hexagonal number.

81581151 is a deficient number, since it is larger than the sum of its proper divisors (29758209).

81581151 is a wasteful number, since it uses less digits than its factorization.

81581151 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2426.

The product of its digits is 1600, while the sum is 30.

The square root of 81581151 is about 9032.2284625667. The cubic root of 81581151 is about 433.7071775169.

Adding to 81581151 its reverse (15118518), we get a palindrome (96699669).

The spelling of 81581151 in words is "eighty-one million, five hundred eighty-one thousand, one hundred fifty-one".