21155188 has 12 divisors (see below), whose sum is σ = 37067940. Its totient is φ = 10564352.

The previous prime is 21155179. The next prime is 21155201. The reversal of 21155188 is 88155112.

It can be written as a sum of positive squares in 2 ways, for example, as 1281424 + 19873764 = 1132^2 + 4458^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 870 + ... + 6562.

It is an arithmetic number, because the mean of its divisors is an integer number (3088995).

Almost surely, 2^21155188 is an apocalyptic number.

It is an amenable number.

21155188 is a deficient number, since it is larger than the sum of its proper divisors (15912752).

21155188 is a wasteful number, since it uses less digits than its factorization.

21155188 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6626 (or 6624 counting only the distinct ones).

The product of its digits is 3200, while the sum is 31.

The square root of 21155188 is about 4599.4769267820. The cubic root of 21155188 is about 276.5703566325.

The spelling of 21155188 in words is "twenty-one million, one hundred fifty-five thousand, one hundred eighty-eight".