57221388 has 216 divisors, whose sum is σ = 189719712. Its totient is φ = 14183424.

The previous prime is 57221387. The next prime is 57221389. The reversal of 57221388 is 88312275.

57221388 is a `hidden beast` number, since 57 + 221 + 388 = 666.

It is an interprime number because it is at equal distance from previous prime (57221387) and next prime (57221389).

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

It is not an unprimeable number, because it can be changed into a prime (57221387) 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, 1546506 + ... + 1546542.

It is an arithmetic number, because the mean of its divisors is an integer number (878332).

Almost surely, 2^57221388 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 57221388, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (94859856).

57221388 is an abundant number, since it is smaller than the sum of its proper divisors (132498324).

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

57221388 is a wasteful number, since it uses less digits than its factorization.

57221388 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 109 (or 85 counting only the distinct ones).

The product of its digits is 26880, while the sum is 36.

The square root of 57221388 is about 7564.4820047377. The cubic root of 57221388 is about 385.3477220581.

It can be divided in two parts, 57 and 221388, that added together give a triangular number (221445 = T₆₆₅).

The spelling of 57221388 in words is "fifty-seven million, two hundred twenty-one thousand, three hundred eighty-eight".