77538821 has 2 divisors, whose sum is σ = 77538822. Its totient is φ = 77538820.

The previous prime is 77538763. The next prime is 77538823. The reversal of 77538821 is 12883577.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 53085796 + 24453025 = 7286^2 + 4945^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-77538821 is a prime.

Together with 77538823, 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 (77538823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38769410 + 38769411.

It is an arithmetic number, because the mean of its divisors is an integer number (38769411).

Almost surely, 2^77538821 is an apocalyptic number.

It is an amenable number.

77538821 is a deficient number, since it is larger than the sum of its proper divisors (1).

77538821 is an equidigital number, since it uses as much as digits as its factorization.

77538821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 94080, while the sum is 41.

The square root of 77538821 is about 8805.6130394198. The cubic root of 77538821 is about 426.4221259699.

The spelling of 77538821 in words is "seventy-seven million, five hundred thirty-eight thousand, eight hundred twenty-one".