28156720 has 20 divisors (see below), whose sum is σ = 65464560. Its totient is φ = 11262656.

The previous prime is 28156717. The next prime is 28156721. The reversal of 28156720 is 2765182.

It is a tau number, because it is divible by the number of its divisors (20).

It is a super-3 number, since 3×28156720³ (a number of 23 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (28156721) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 175900 + ... + 176059.

It is an arithmetic number, because the mean of its divisors is an integer number (3273228).

Almost surely, 2^28156720 is an apocalyptic number.

28156720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

28156720 is an abundant number, since it is smaller than the sum of its proper divisors (37307840).

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

28156720 is a wasteful number, since it uses less digits than its factorization.

28156720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 351972 (or 351966 counting only the distinct ones).

The product of its (nonzero) digits is 6720, while the sum is 31.

The square root of 28156720 is about 5306.2906064406. The cubic root of 28156720 is about 304.2243842014.

The spelling of 28156720 in words is "twenty-eight million, one hundred fifty-six thousand, seven hundred twenty".