77280221 has 4 divisors (see below), whose sum is σ = 78211392. Its totient is φ = 76349052.

The previous prime is 77280199. The next prime is 77280223. The reversal of 77280221 is 12208277.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 77280221 - 2¹⁰ = 77279197 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 (77280223) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 465461 + ... + 465626.

It is an arithmetic number, because the mean of its divisors is an integer number (19552848).

Almost surely, 2^77280221 is an apocalyptic number.

It is an amenable number.

77280221 is a deficient number, since it is larger than the sum of its proper divisors (931171).

77280221 is an equidigital number, since it uses as much as digits as its factorization.

77280221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 931170.

The product of its (nonzero) digits is 3136, while the sum is 29.

The square root of 77280221 is about 8790.9169601356. The cubic root of 77280221 is about 425.9475439977.

Adding to 77280221 its reverse (12208277), we get a palindrome (89488498).

The spelling of 77280221 in words is "seventy-seven million, two hundred eighty thousand, two hundred twenty-one".