81929551 has 4 divisors (see below), whose sum is σ = 89377704. Its totient is φ = 74481400.

The previous prime is 81929509. The next prime is 81929569. The reversal of 81929551 is 15592918.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81929551 is a prime.

It is a super-3 number, since 3×81929551³ (a number of 25 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81929591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3724060 + ... + 3724081.

It is an arithmetic number, because the mean of its divisors is an integer number (22344426).

Almost surely, 2^81929551 is an apocalyptic number.

81929551 is a deficient number, since it is larger than the sum of its proper divisors (7448153).

81929551 is a wasteful number, since it uses less digits than its factorization.

81929551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7448152.

The product of its digits is 32400, while the sum is 40.

The square root of 81929551 is about 9051.4944070026. The cubic root of 81929551 is about 434.3236965166.

The spelling of 81929551 in words is "eighty-one million, nine hundred twenty-nine thousand, five hundred fifty-one".