77656721 has 8 divisors (see below), whose sum is σ = 79161600. Its totient is φ = 76159440.

The previous prime is 77656687. The next prime is 77656727. The reversal of 77656721 is 12765677.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-77656721 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (77656727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 21440 + ... + 24798.

It is an arithmetic number, because the mean of its divisors is an integer number (9895200).

Almost surely, 2^77656721 is an apocalyptic number.

It is an amenable number.

77656721 is a deficient number, since it is larger than the sum of its proper divisors (1504879).

77656721 is a wasteful number, since it uses less digits than its factorization.

77656721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3799.

The product of its digits is 123480, while the sum is 41.

The square root of 77656721 is about 8812.3050900431. The cubic root of 77656721 is about 426.6381455409.

The spelling of 77656721 in words is "seventy-seven million, six hundred fifty-six thousand, seven hundred twenty-one".