77221721 has 8 divisors (see below), whose sum is σ = 78681984. Its totient is φ = 75770640.

The previous prime is 77221717. The next prime is 77221723. The reversal of 77221721 is 12712277.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 77221721 - 2² = 77221717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (77221723) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16031 + ... + 20283.

It is an arithmetic number, because the mean of its divisors is an integer number (9835248).

Almost surely, 2^77221721 is an apocalyptic number.

It is an amenable number.

77221721 is a deficient number, since it is larger than the sum of its proper divisors (1460263).

77221721 is a wasteful number, since it uses less digits than its factorization.

77221721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4591.

The product of its digits is 2744, while the sum is 29.

The square root of 77221721 is about 8787.5890322659. The cubic root of 77221721 is about 425.8400381738.

Adding to 77221721 its reverse (12712277), we get a palindrome (89933998).

The spelling of 77221721 in words is "seventy-seven million, two hundred twenty-one thousand, seven hundred twenty-one".