21155284 has 24 divisors (see below), whose sum is σ = 39160800. Its totient is φ = 9972000.

The previous prime is 21155263. The next prime is 21155287. The reversal of 21155284 is 48255112.

It is a super-2 number, since 2×21155284² = 895092082241312, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21155287) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18522 + ... + 19630.

It is an arithmetic number, because the mean of its divisors is an integer number (1631700).

Almost surely, 2^21155284 is an apocalyptic number.

It is an amenable number.

21155284 is a deficient number, since it is larger than the sum of its proper divisors (18005516).

21155284 is a wasteful number, since it uses less digits than its factorization.

21155284 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1383 (or 1381 counting only the distinct ones).

The product of its digits is 3200, while the sum is 28.

The square root of 21155284 is about 4599.4873627395. The cubic root of 21155284 is about 276.5707749809.

The spelling of 21155284 in words is "twenty-one million, one hundred fifty-five thousand, two hundred eighty-four".