81261599 has 4 divisors (see below), whose sum is σ = 84794736. Its totient is φ = 77728464.

The previous prime is 81261589. The next prime is 81261617. The reversal of 81261599 is 99516218.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 81261599 - 2¹² = 81257503 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 (81261569) 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, 1766534 + ... + 1766579.

It is an arithmetic number, because the mean of its divisors is an integer number (21198684).

Almost surely, 2^81261599 is an apocalyptic number.

81261599 is a deficient number, since it is larger than the sum of its proper divisors (3533137).

81261599 is a wasteful number, since it uses less digits than its factorization.

81261599 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3533136.

The product of its digits is 38880, while the sum is 41.

The square root of 81261599 is about 9014.5215624569. The cubic root of 81261599 is about 433.1401619613.

The spelling of 81261599 in words is "eighty-one million, two hundred sixty-one thousand, five hundred ninety-nine".