28720131 has 16 divisors (see below), whose sum is σ = 42795648. Its totient is φ = 16980800.

The previous prime is 28720129. The next prime is 28720141. The reversal of 28720131 is 13102782.

It is a cyclic number.

It is not a de Polignac number, because 28720131 - 2¹ = 28720129 is a prime.

It is a super-2 number, since 2×28720131² = 1649691849314322, which contains 22 as substring.

It is a Smith number, since the sum of its digits (24) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (28720141) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9261 + ... + 11966.

It is an arithmetic number, because the mean of its divisors is an integer number (2674728).

Almost surely, 2^28720131 is an apocalyptic number.

28720131 is a deficient number, since it is larger than the sum of its proper divisors (14075517).

28720131 is a wasteful number, since it uses less digits than its factorization.

28720131 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21282.

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 28720131 is about 5359.1166249672. The cubic root of 28720131 is about 306.2401570625.

The spelling of 28720131 in words is "twenty-eight million, seven hundred twenty thousand, one hundred thirty-one".