77780721 has 4 divisors (see below), whose sum is σ = 103707632. Its totient is φ = 51853812.

The previous prime is 77780707. The next prime is 77780741. The reversal of 77780721 is 12708777.

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 not a de Polignac number, because 77780721 - 2⁶ = 77780657 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 77780721.

It is not an unprimeable number, because it can be changed into a prime (77780741) 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, 12963451 + ... + 12963456.

It is an arithmetic number, because the mean of its divisors is an integer number (25926908).

Almost surely, 2^77780721 is an apocalyptic number.

It is an amenable number.

77780721 is a deficient number, since it is larger than the sum of its proper divisors (25926911).

77780721 is a wasteful number, since it uses less digits than its factorization.

77780721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25926910.

The product of its (nonzero) digits is 38416, while the sum is 39.

The square root of 77780721 is about 8819.3379003188. The cubic root of 77780721 is about 426.8651059218.

The spelling of 77780721 in words is "seventy-seven million, seven hundred eighty thousand, seven hundred twenty-one".