81790551 has 6 divisors (see below), whose sum is σ = 118141920. Its totient is φ = 54527028.

The previous prime is 81790547. The next prime is 81790559. The reversal of 81790551 is 15509718.

81790551 is a `hidden beast` number, since 8 + 17 + 90 + 551 = 666.

It is not a de Polignac number, because 81790551 - 2² = 81790547 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81790559) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4543911 + ... + 4543928.

It is an arithmetic number, because the mean of its divisors is an integer number (19690320).

Almost surely, 2^81790551 is an apocalyptic number.

81790551 is a deficient number, since it is larger than the sum of its proper divisors (36351369).

81790551 is a wasteful number, since it uses less digits than its factorization.

81790551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9087845 (or 9087842 counting only the distinct ones).

The product of its (nonzero) digits is 12600, while the sum is 36.

The square root of 81790551 is about 9043.8128574180. The cubic root of 81790551 is about 434.0779359142.

The spelling of 81790551 in words is "eighty-one million, seven hundred ninety thousand, five hundred fifty-one".