77821217 has 2 divisors, whose sum is σ = 77821218. Its totient is φ = 77821216.

The previous prime is 77821199. The next prime is 77821229. The reversal of 77821217 is 71212877.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 69288976 + 8532241 = 8324^2 + 2921^2 .

It is a cyclic number.

It is not a de Polignac number, because 77821217 - 2⁶ = 77821153 is a prime.

It is a super-2 number, since 2×77821217² = 12112283630722178, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (77821417) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 38910608 + 38910609.

It is an arithmetic number, because the mean of its divisors is an integer number (38910609).

Almost surely, 2^77821217 is an apocalyptic number.

It is an amenable number.

77821217 is a deficient number, since it is larger than the sum of its proper divisors (1).

77821217 is an equidigital number, since it uses as much as digits as its factorization.

77821217 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10976, while the sum is 35.

The square root of 77821217 is about 8821.6334655210. The cubic root of 77821217 is about 426.9391745341.

The spelling of 77821217 in words is "seventy-seven million, eight hundred twenty-one thousand, two hundred seventeen".