81555691 has 8 divisors (see below), whose sum is σ = 93801440. Its totient is φ = 69458688.

The previous prime is 81555679. The next prime is 81555701. The reversal of 81555691 is 19655518.

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 81555691 - 2⁹ = 81555179 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81555611) 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, 36006 + ... + 38203.

It is an arithmetic number, because the mean of its divisors is an integer number (11725180).

Almost surely, 2^81555691 is an apocalyptic number.

81555691 is a deficient number, since it is larger than the sum of its proper divisors (12245749).

81555691 is a wasteful number, since it uses less digits than its factorization.

81555691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74373.

The product of its digits is 54000, while the sum is 40.

The square root of 81555691 is about 9030.8189551114. The cubic root of 81555691 is about 433.6620554370.

The spelling of 81555691 in words is "eighty-one million, five hundred fifty-five thousand, six hundred ninety-one".