81159551 has 4 divisors (see below), whose sum is σ = 88537704. Its totient is φ = 73781400.

The previous prime is 81159539. The next prime is 81159577. The reversal of 81159551 is 15595118.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 81159551 - 2²² = 76965247 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81159521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3689060 + ... + 3689081.

It is an arithmetic number, because the mean of its divisors is an integer number (22134426).

Almost surely, 2^81159551 is an apocalyptic number.

81159551 is a deficient number, since it is larger than the sum of its proper divisors (7378153).

81159551 is a wasteful number, since it uses less digits than its factorization.

81159551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7378152.

The product of its digits is 9000, while the sum is 35.

The square root of 81159551 is about 9008.8595837653. The cubic root of 81159551 is about 432.9587741011.

The spelling of 81159551 in words is "eighty-one million, one hundred fifty-nine thousand, five hundred fifty-one".