81993777 has 4 divisors (see below), whose sum is σ = 109325040. Its totient is φ = 54662516.

The previous prime is 81993767. The next prime is 81993823. The reversal of 81993777 is 77739918.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81993777 - 2⁶ = 81993713 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81993757) 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, 13665627 + ... + 13665632.

It is an arithmetic number, because the mean of its divisors is an integer number (27331260).

Almost surely, 2^81993777 is an apocalyptic number.

It is an amenable number.

81993777 is a deficient number, since it is larger than the sum of its proper divisors (27331263).

81993777 is a wasteful number, since it uses less digits than its factorization.

81993777 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 27331262.

The product of its digits is 666792, while the sum is 51.

The square root of 81993777 is about 9055.0415239247. The cubic root of 81993777 is about 434.4371581735.

The spelling of 81993777 in words is "eighty-one million, nine hundred ninety-three thousand, seven hundred seventy-seven".