28661220 has 216 divisors, whose sum is σ = 106282176. Its totient is φ = 6120576.

The previous prime is 28661219. The next prime is 28661221. The reversal of 28661220 is 2216682.

28661220 is a `hidden beast` number, since 28 + 6 + 612 + 20 = 666.

It is an interprime number because it is at equal distance from previous prime (28661219) and next prime (28661221).

It is not an unprimeable number, because it can be changed into a prime (28661221) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 666519 + ... + 666561.

Almost surely, 2^28661220 is an apocalyptic number.

28661220 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 28661220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (53141088).

28661220 is an abundant number, since it is smaller than the sum of its proper divisors (77620956).

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

28661220 is a wasteful number, since it uses less digits than its factorization.

28661220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 111 (or 83 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 27.

The square root of 28661220 is about 5353.6174685907. The cubic root of 28661220 is about 306.0306261798.

The spelling of 28661220 in words is "twenty-eight million, six hundred sixty-one thousand, two hundred twenty".