81669977 has 2 divisors, whose sum is σ = 81669978. Its totient is φ = 81669976.

The previous prime is 81669971. The next prime is 81670007. The reversal of 81669977 is 77996618.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 78783376 + 2886601 = 8876^2 + 1699^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81669977 is a prime.

It is not a weakly prime, because it can be changed into another prime (81669971) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40834988 + 40834989.

It is an arithmetic number, because the mean of its divisors is an integer number (40834989).

Almost surely, 2^81669977 is an apocalyptic number.

It is an amenable number.

81669977 is a deficient number, since it is larger than the sum of its proper divisors (1).

81669977 is an equidigital number, since it uses as much as digits as its factorization.

81669977 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1143072, while the sum is 53.

The square root of 81669977 is about 9037.1442945214. The cubic root of 81669977 is about 433.8645279990.

The spelling of 81669977 in words is "eighty-one million, six hundred sixty-nine thousand, nine hundred seventy-seven".