77399821 has 2 divisors, whose sum is σ = 77399822. Its totient is φ = 77399820.

The previous prime is 77399813. The next prime is 77399831. The reversal of 77399821 is 12899377.

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., 46430596 + 30969225 = 6814^2 + 5565^2 .

It is a cyclic number.

It is not a de Polignac number, because 77399821 - 2³ = 77399813 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (77399831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38699910 + 38699911.

It is an arithmetic number, because the mean of its divisors is an integer number (38699911).

Almost surely, 2^77399821 is an apocalyptic number.

It is an amenable number.

77399821 is a deficient number, since it is larger than the sum of its proper divisors (1).

77399821 is an equidigital number, since it uses as much as digits as its factorization.

77399821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 190512, while the sum is 46.

The square root of 77399821 is about 8797.7168060810. The cubic root of 77399821 is about 426.1671649561.

The spelling of 77399821 in words is "seventy-seven million, three hundred ninety-nine thousand, eight hundred twenty-one".