77021521 has 2 divisors, whose sum is σ = 77021522. Its totient is φ = 77021520.

The previous prime is 77021507. The next prime is 77021587. The reversal of 77021521 is 12512077.

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., 53363025 + 23658496 = 7305^2 + 4864^2 .

It is an emirp because it is prime and its reverse (12512077) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 77021521 - 2⁷ = 77021393 is a prime.

It is not a weakly prime, because it can be changed into another prime (77021501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38510760 + 38510761.

It is an arithmetic number, because the mean of its divisors is an integer number (38510761).

Almost surely, 2^77021521 is an apocalyptic number.

It is an amenable number.

77021521 is a deficient number, since it is larger than the sum of its proper divisors (1).

77021521 is an equidigital number, since it uses as much as digits as its factorization.

77021521 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 980, while the sum is 25.

The square root of 77021521 is about 8776.1905745033. The cubic root of 77021521 is about 425.4717179880.

Adding to 77021521 its reverse (12512077), we get a palindrome (89533598).

The spelling of 77021521 in words is "seventy-seven million, twenty-one thousand, five hundred twenty-one".