28720778 has 16 divisors (see below), whose sum is σ = 43913664. Its totient is φ = 14085120.

The previous prime is 28720777. The next prime is 28720789. The reversal of 28720778 is 87702782.

It is not an unprimeable number, because it can be changed into a prime (28720777) 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, 36101 + ... + 36887.

It is an arithmetic number, because the mean of its divisors is an integer number (2744604).

Almost surely, 2^28720778 is an apocalyptic number.

28720778 is a deficient number, since it is larger than the sum of its proper divisors (15192886).

28720778 is a wasteful number, since it uses less digits than its factorization.

28720778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1117.

The product of its (nonzero) digits is 87808, while the sum is 41.

The square root of 28720778 is about 5359.1769890534. The cubic root of 28720778 is about 306.2424566794.

The spelling of 28720778 in words is "twenty-eight million, seven hundred twenty thousand, seven hundred seventy-eight".