28191780 has 192 divisors, whose sum is σ = 96526080. Its totient is φ = 6801408.

The previous prime is 28191773. The next prime is 28191829. The reversal of 28191780 is 8719182.

28191780 = T₂₈₀ + T₂₈₁ + ... + T₅₇₅.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 339619 + ... + 339701.

It is an arithmetic number, because the mean of its divisors is an integer number (502740).

Almost surely, 2^28191780 is an apocalyptic number.

28191780 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 28191780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (48263040).

28191780 is an abundant number, since it is smaller than the sum of its proper divisors (68334300).

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

28191780 is a wasteful number, since it uses less digits than its factorization.

28191780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 155 (or 147 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 36.

The square root of 28191780 is about 5309.5932047568. The cubic root of 28191780 is about 304.3506025360.

The spelling of 28191780 in words is "twenty-eight million, one hundred ninety-one thousand, seven hundred eighty".