21557056 has 14 divisors (see below), whose sum is σ = 42777410. Its totient is φ = 10778496.

The previous prime is 21557047. The next prime is 21557057. The reversal of 21557056 is 65075512.

It can be written as a sum of positive squares in only one way, i.e., 16646400 + 4910656 = 4080^2 + 2216^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21557057) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 168351 + ... + 168478.

Almost surely, 2^21557056 is an apocalyptic number.

It is an amenable number.

21557056 is a deficient number, since it is larger than the sum of its proper divisors (21220354).

21557056 is an equidigital number, since it uses as much as digits as its factorization.

21557056 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 336841 (or 336831 counting only the distinct ones).

The product of its (nonzero) digits is 10500, while the sum is 31.

The square root of 21557056 is about 4642.9576780324. The cubic root of 21557056 is about 278.3106442435.

The spelling of 21557056 in words is "twenty-one million, five hundred fifty-seven thousand, fifty-six".