28991820 has 192 divisors, whose sum is σ = 99348480. Its totient is φ = 6220800.

The previous prime is 28991813. The next prime is 28991857. The reversal of 28991820 is 2819982.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 265926 + ... + 266034.

It is an arithmetic number, because the mean of its divisors is an integer number (517440).

Almost surely, 2^28991820 is an apocalyptic number.

28991820 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 28991820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (49674240).

28991820 is an abundant number, since it is smaller than the sum of its proper divisors (70356660).

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

28991820 is a wasteful number, since it uses less digits than its factorization.

28991820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 176 (or 174 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 39.

The square root of 28991820 is about 5384.4052596364. The cubic root of 28991820 is about 307.2027930112.

The spelling of 28991820 in words is "twenty-eight million, nine hundred ninety-one thousand, eight hundred twenty".