81929819 has 4 divisors (see below), whose sum is σ = 83318520. Its totient is φ = 80541120.

The previous prime is 81929777. The next prime is 81929821. The reversal of 81929819 is 91892918.

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 81929819 - 2¹⁶ = 81864283 is a prime.

It is a super-2 number, since 2×81929819² = 13424990482745522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81929879) 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, 694262 + ... + 694379.

It is an arithmetic number, because the mean of its divisors is an integer number (20829630).

Almost surely, 2^81929819 is an apocalyptic number.

81929819 is a deficient number, since it is larger than the sum of its proper divisors (1388701).

81929819 is a wasteful number, since it uses less digits than its factorization.

81929819 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1388700.

The product of its digits is 93312, while the sum is 47.

The square root of 81929819 is about 9051.5092111758. The cubic root of 81929819 is about 434.3241700886.

The spelling of 81929819 in words is "eighty-one million, nine hundred twenty-nine thousand, eight hundred nineteen".