77231981 has 2 divisors, whose sum is σ = 77231982. Its totient is φ = 77231980.

The previous prime is 77231963. The next prime is 77232013. The reversal of 77231981 is 18913277.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 66275881 + 10956100 = 8141^2 + 3310^2 .

It is an emirp because it is prime and its reverse (18913277) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 77231981 - 2¹⁴ = 77215597 is a prime.

It is a super-2 number, since 2×77231981² = 11929557778368722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (77231081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38615990 + 38615991.

It is an arithmetic number, because the mean of its divisors is an integer number (38615991).

Almost surely, 2^77231981 is an apocalyptic number.

It is an amenable number.

77231981 is a deficient number, since it is larger than the sum of its proper divisors (1).

77231981 is an equidigital number, since it uses as much as digits as its factorization.

77231981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 21168, while the sum is 38.

The square root of 77231981 is about 8788.1727907455. The cubic root of 77231981 is about 425.8588969666.

The spelling of 77231981 in words is "seventy-seven million, two hundred thirty-one thousand, nine hundred eighty-one".