77121557 has 2 divisors, whose sum is σ = 77121558. Its totient is φ = 77121556.

The previous prime is 77121491. The next prime is 77121581. The reversal of 77121557 is 75512177.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 40627876 + 36493681 = 6374^2 + 6041^2 .

It is a cyclic number.

It is not a de Polignac number, because 77121557 - 2²⁰ = 76072981 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (77120557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38560778 + 38560779.

It is an arithmetic number, because the mean of its divisors is an integer number (38560779).

Almost surely, 2^77121557 is an apocalyptic number.

It is an amenable number.

77121557 is a deficient number, since it is larger than the sum of its proper divisors (1).

77121557 is an equidigital number, since it uses as much as digits as its factorization.

77121557 is an evil number, because the sum of its binary digits is even.

The product of its digits is 17150, while the sum is 35.

The square root of 77121557 is about 8781.8880088509. Note that the first 3 decimals coincide. The cubic root of 77121557 is about 425.6558400131.

The spelling of 77121557 in words is "seventy-seven million, one hundred twenty-one thousand, five hundred fifty-seven".