77680021 has 6 divisors (see below), whose sum is σ = 82518530. Its totient is φ = 73110336.

The previous prime is 77680003. The next prime is 77680051. The reversal of 77680021 is 12008677.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 7623121 + 70056900 = 2761^2 + 8370^2 .

It is not a de Polignac number, because 77680021 - 2²¹ = 75582869 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (77680051) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 134106 + ... + 134683.

Almost surely, 2^77680021 is an apocalyptic number.

It is an amenable number.

77680021 is a deficient number, since it is larger than the sum of its proper divisors (4838509).

77680021 is a wasteful number, since it uses less digits than its factorization.

77680021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 268823 (or 268806 counting only the distinct ones).

The product of its (nonzero) digits is 4704, while the sum is 31.

The square root of 77680021 is about 8813.6270059494. The cubic root of 77680021 is about 426.6808105527.

Adding to 77680021 its reverse (12008677), we get a palindrome (89688698).

The spelling of 77680021 in words is "seventy-seven million, six hundred eighty thousand, twenty-one".