21155636 has 6 divisors (see below), whose sum is σ = 37022370. Its totient is φ = 10577816.

The previous prime is 21155627. The next prime is 21155663. The reversal of 21155636 is 63655112.

It can be written as a sum of positive squares in only one way, i.e., 16048036 + 5107600 = 4006^2 + 2260^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21155599 and 21155608.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2644451 + ... + 2644458.

It is an arithmetic number, because the mean of its divisors is an integer number (6170395).

Almost surely, 2^21155636 is an apocalyptic number.

It is an amenable number.

21155636 is a deficient number, since it is larger than the sum of its proper divisors (15866734).

21155636 is a wasteful number, since it uses less digits than its factorization.

21155636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5288913 (or 5288911 counting only the distinct ones).

The product of its digits is 5400, while the sum is 29.

The square root of 21155636 is about 4599.5256277142. The cubic root of 21155636 is about 276.5723089140.

The spelling of 21155636 in words is "twenty-one million, one hundred fifty-five thousand, six hundred thirty-six".