28721975 has 6 divisors (see below), whose sum is σ = 35615280. Its totient is φ = 22977560.

The previous prime is 28721971. The next prime is 28721981. The reversal of 28721975 is 57912782.

It is not a de Polignac number, because 28721975 - 2² = 28721971 is a prime.

It is a congruent number.

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 5 ways as a sum of consecutive naturals, for example, 574415 + ... + 574464.

It is an arithmetic number, because the mean of its divisors is an integer number (5935880).

Almost surely, 2^28721975 is an apocalyptic number.

28721975 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

28721975 is a deficient number, since it is larger than the sum of its proper divisors (6893305).

28721975 is a wasteful number, since it uses less digits than its factorization.

28721975 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1148889 (or 1148884 counting only the distinct ones).

The product of its digits is 70560, while the sum is 41.

The square root of 28721975 is about 5359.2886654854. The cubic root of 28721975 is about 306.2467110573.

The spelling of 28721975 in words is "twenty-eight million, seven hundred twenty-one thousand, nine hundred seventy-five".