28720840 has 32 divisors (see below), whose sum is σ = 64800000. Its totient is φ = 11456704.

The previous prime is 28720831. The next prime is 28720847. The reversal of 28720840 is 4802782.

It is not an unprimeable number, because it can be changed into a prime (28720847) 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, 18411 + ... + 19909.

It is an arithmetic number, because the mean of its divisors is an integer number (2025000).

Almost surely, 2^28720840 is an apocalyptic number.

28720840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

28720840 is an abundant number, since it is smaller than the sum of its proper divisors (36079160).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

28720840 is a wasteful number, since it uses less digits than its factorization.

28720840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1989 (or 1985 counting only the distinct ones).

The product of its (nonzero) digits is 7168, while the sum is 31.

The square root of 28720840 is about 5359.1827735206. The cubic root of 28720840 is about 306.2426770427.

The spelling of 28720840 in words is "twenty-eight million, seven hundred twenty thousand, eight hundred forty".