28161720 has 96 divisors (see below), whose sum is σ = 92355120. Its totient is φ = 7441920.

The previous prime is 28161701. The next prime is 28161767. The reversal of 28161720 is 2716182.

28161720 is a `hidden beast` number, since 28 + 1 + 617 + 20 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 49035 + ... + 49605.

Almost surely, 2^28161720 is an apocalyptic number.

28161720 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 28161720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (46177560).

28161720 is an abundant number, since it is smaller than the sum of its proper divisors (64193400).

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

28161720 is a wasteful number, since it uses less digits than its factorization.

28161720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 725 (or 718 counting only the distinct ones).

The product of its (nonzero) digits is 1344, while the sum is 27.

The square root of 28161720 is about 5306.7617244418. The cubic root of 28161720 is about 304.2423909377.

It can be divided in two parts, 281 and 61720, that added together give a square (62001 = 249²).

The spelling of 28161720 in words is "twenty-eight million, one hundred sixty-one thousand, seven hundred twenty".