21002536 has 8 divisors (see below), whose sum is σ = 39379770. Its totient is φ = 10501264.

The previous prime is 21002521. The next prime is 21002539. The reversal of 21002536 is 63520012.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 20520900 + 481636 = 4530^2 + 694^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a super-2 number, since 2×21002536² = 882213036862592, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21002539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1312651 + ... + 1312666.

Almost surely, 2^21002536 is an apocalyptic number.

It is an amenable number.

21002536 is a deficient number, since it is larger than the sum of its proper divisors (18377234).

21002536 is a wasteful number, since it uses less digits than its factorization.

21002536 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2625323 (or 2625319 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 19.

The square root of 21002536 is about 4582.8523868875. The cubic root of 21002536 is about 275.9035229557.

Adding to 21002536 its reverse (63520012), we get a palindrome (84522548).

The spelling of 21002536 in words is "twenty-one million, two thousand, five hundred thirty-six".