21555536 has 10 divisors (see below), whose sum is σ = 41763882. Its totient is φ = 10777760.

The previous prime is 21555511. The next prime is 21555539. The reversal of 21555536 is 63555512.

It can be written as a sum of positive squares in only one way, i.e., 15523600 + 6031936 = 3940^2 + 2456^2 .

It is a super-2 number, since 2×21555536² = 929282264494592, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21555539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 673595 + ... + 673626.

Almost surely, 2^21555536 is an apocalyptic number.

It is an amenable number.

21555536 is a deficient number, since it is larger than the sum of its proper divisors (20208346).

21555536 is a wasteful number, since it uses less digits than its factorization.

21555536 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1347229 (or 1347223 counting only the distinct ones).

The product of its digits is 22500, while the sum is 32.

The square root of 21555536 is about 4642.7939863836. The cubic root of 21555536 is about 278.3041028104.

The spelling of 21555536 in words is "twenty-one million, five hundred fifty-five thousand, five hundred thirty-six".