28720505 has 8 divisors (see below), whose sum is σ = 37597824. Its totient is φ = 20887600.

The previous prime is 28720487. The next prime is 28720507. The reversal of 28720505 is 50502782.

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

It is not a de Polignac number, because 28720505 - 2⁶ = 28720441 is a prime.

It is not an unprimeable number, because it can be changed into a prime (28720507) 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, 261041 + ... + 261150.

It is an arithmetic number, because the mean of its divisors is an integer number (4699728).

Almost surely, 2^28720505 is an apocalyptic number.

It is an amenable number.

28720505 is a deficient number, since it is larger than the sum of its proper divisors (8877319).

28720505 is a wasteful number, since it uses less digits than its factorization.

28720505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 522207.

The product of its (nonzero) digits is 5600, while the sum is 29.

The square root of 28720505 is about 5359.1515186641. The cubic root of 28720505 is about 306.2414863661.

The spelling of 28720505 in words is "twenty-eight million, seven hundred twenty thousand, five hundred five".