77648981 has 2 divisors, whose sum is σ = 77648982. Its totient is φ = 77648980.

The previous prime is 77648939. The next prime is 77648983. The reversal of 77648981 is 18984677.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 56175025 + 21473956 = 7495^2 + 4634^2 .

It is an emirp because it is prime and its reverse (18984677) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 77648981 - 2²² = 73454677 is a prime.

It is a super-2 number, since 2×77648981² = 12058728500676722, which contains 22 as substring.

Together with 77648983, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (77648983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38824490 + 38824491.

It is an arithmetic number, because the mean of its divisors is an integer number (38824491).

Almost surely, 2^77648981 is an apocalyptic number.

It is an amenable number.

77648981 is a deficient number, since it is larger than the sum of its proper divisors (1).

77648981 is an equidigital number, since it uses as much as digits as its factorization.

77648981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 677376, while the sum is 50.

The square root of 77648981 is about 8811.8659204507. The cubic root of 77648981 is about 426.6239708117.

The spelling of 77648981 in words is "seventy-seven million, six hundred forty-eight thousand, nine hundred eighty-one".