77781889 has 2 divisors, whose sum is σ = 77781890. Its totient is φ = 77781888.

The previous prime is 77781871. The next prime is 77781923. The reversal of 77781889 is 98818777.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 76860289 + 921600 = 8767^2 + 960^2 .

It is an emirp because it is prime and its reverse (98818777) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 77781889 - 2²³ = 69393281 is a prime.

It is not a weakly prime, because it can be changed into another prime (77781829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38890944 + 38890945.

It is an arithmetic number, because the mean of its divisors is an integer number (38890945).

Almost surely, 2^77781889 is an apocalyptic number.

It is an amenable number.

77781889 is a deficient number, since it is larger than the sum of its proper divisors (1).

77781889 is an equidigital number, since it uses as much as digits as its factorization.

77781889 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1580544, while the sum is 55.

The square root of 77781889 is about 8819.4041181930. The cubic root of 77781889 is about 426.8672425950.

The spelling of 77781889 in words is "seventy-seven million, seven hundred eighty-one thousand, eight hundred eighty-nine".