77939809 has 2 divisors, whose sum is σ = 77939810. Its totient is φ = 77939808.

The previous prime is 77939789. The next prime is 77939819. The reversal of 77939809 is 90893977.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 68939809 + 9000000 = 8303^2 + 3000^2 .

It is an emirp because it is prime and its reverse (90893977) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 77939809 - 2⁷ = 77939681 is a prime.

It is a super-2 number, since 2×77939809² = 12149227653912962, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (77939819) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38969904 + 38969905.

It is an arithmetic number, because the mean of its divisors is an integer number (38969905).

Almost surely, 2^77939809 is an apocalyptic number.

It is an amenable number.

77939809 is a deficient number, since it is larger than the sum of its proper divisors (1).

77939809 is an equidigital number, since it uses as much as digits as its factorization.

77939809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 857304, while the sum is 52.

The square root of 77939809 is about 8828.3525643237. The cubic root of 77939809 is about 427.1559357854.

The spelling of 77939809 in words is "seventy-seven million, nine hundred thirty-nine thousand, eight hundred nine".