81978767 has 4 divisors (see below), whose sum is σ = 88284840. Its totient is φ = 75672696.

The previous prime is 81978761. The next prime is 81978773. The reversal of 81978767 is 76787918.

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

It is an interprime number because it is at equal distance from previous prime (81978761) and next prime (81978773).

It is a cyclic number.

It is not a de Polignac number, because 81978767 - 2⁴ = 81978751 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81978761) 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, 3153017 + ... + 3153042.

It is an arithmetic number, because the mean of its divisors is an integer number (22071210).

Almost surely, 2^81978767 is an apocalyptic number.

81978767 is a deficient number, since it is larger than the sum of its proper divisors (6306073).

81978767 is a wasteful number, since it uses less digits than its factorization.

81978767 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6306072.

The product of its digits is 1185408, while the sum is 53.

The square root of 81978767 is about 9054.2126659362. The cubic root of 81978767 is about 434.4106468132.

The spelling of 81978767 in words is "eighty-one million, nine hundred seventy-eight thousand, seven hundred sixty-seven".