28721979 has 64 divisors (see below), whose sum is σ = 51448320. Its totient is φ = 15603840.

The previous prime is 28721971. The next prime is 28721981. The reversal of 28721979 is 97912782.

It is not a de Polignac number, because 28721979 - 2³ = 28721971 is a prime.

It is not an unprimeable number, because it can be changed into a prime (28721971) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 165937 + ... + 166109.

It is an arithmetic number, because the mean of its divisors is an integer number (803880).

Almost surely, 2^28721979 is an apocalyptic number.

28721979 is a deficient number, since it is larger than the sum of its proper divisors (22726341).

28721979 is a wasteful number, since it uses less digits than its factorization.

28721979 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 249 (or 243 counting only the distinct ones).

The product of its digits is 127008, while the sum is 45.

The square root of 28721979 is about 5359.2890386692. The cubic root of 28721979 is about 306.2467252739.

It can be divided in two parts, 2872 and 1979, that added together give a triangular number (4851 = T₉₈).

The spelling of 28721979 in words is "twenty-eight million, seven hundred twenty-one thousand, nine hundred seventy-nine".