28921780 has 12 divisors (see below), whose sum is σ = 60735780. Its totient is φ = 11568704.

The previous prime is 28921771. The next prime is 28921807. The reversal of 28921780 is 8712982.

It can be written as a sum of positive squares in 2 ways, for example, as 16048036 + 12873744 = 4006^2 + 3588^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 723025 + ... + 723064.

It is an arithmetic number, because the mean of its divisors is an integer number (5061315).

Almost surely, 2^28921780 is an apocalyptic number.

28921780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

28921780 is an abundant number, since it is smaller than the sum of its proper divisors (31814000).

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

28921780 is a wasteful number, since it uses less digits than its factorization.

28921780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1446098 (or 1446096 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 37.

The square root of 28921780 is about 5377.8973586338. The cubic root of 28921780 is about 306.9552078439.

The spelling of 28921780 in words is "twenty-eight million, nine hundred twenty-one thousand, seven hundred eighty".