78928221 has 8 divisors (see below), whose sum is σ = 106322944. Its totient is φ = 52076160.

The previous prime is 78928217. The next prime is 78928237. The reversal of 78928221 is 12282987.

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

It is not a de Polignac number, because 78928221 - 2² = 78928217 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 78928221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (78928621) 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, 135325 + ... + 135906.

It is an arithmetic number, because the mean of its divisors is an integer number (13290368).

Almost surely, 2^78928221 is an apocalyptic number.

It is an amenable number.

78928221 is a deficient number, since it is larger than the sum of its proper divisors (27394723).

78928221 is a wasteful number, since it uses less digits than its factorization.

78928221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 271331.

The product of its digits is 32256, while the sum is 39.

The square root of 78928221 is about 8884.1556154764. The cubic root of 78928221 is about 428.9540487945.

The spelling of 78928221 in words is "seventy-eight million, nine hundred twenty-eight thousand, two hundred twenty-one".