81647899 has 4 divisors (see below), whose sum is σ = 81814680. Its totient is φ = 81481120.

The previous prime is 81647887. The next prime is 81647903. The reversal of 81647899 is 99874618.

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 81647899 - 2⁷ = 81647771 is a prime.

It is a super-2 number, since 2×81647899² = 13332758822228402, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81647849) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 82654 + ... + 83635.

It is an arithmetic number, because the mean of its divisors is an integer number (20453670).

Almost surely, 2^81647899 is an apocalyptic number.

81647899 is a deficient number, since it is larger than the sum of its proper divisors (166781).

81647899 is a wasteful number, since it uses less digits than its factorization.

81647899 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 166780.

The product of its digits is 870912, while the sum is 52.

The square root of 81647899 is about 9035.9226977658. The cubic root of 81647899 is about 433.8254286682.

The spelling of 81647899 in words is "eighty-one million, six hundred forty-seven thousand, eight hundred ninety-nine".