21000736 has 12 divisors (see below), whose sum is σ = 41345262. Its totient is φ = 10500352.

The previous prime is 21000731. The next prime is 21000737. The reversal of 21000736 is 63700012.

It can be written as a sum of positive squares in only one way, i.e., 20976400 + 24336 = 4580^2 + 156^2 .

It is a super-4 number, since 4×21000736⁴ (a number of 30 digits) contains 4444 as substring.

It is not an unprimeable number, because it can be changed into a prime (21000731) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 328105 + ... + 328168.

Almost surely, 2^21000736 is an apocalyptic number.

It is an amenable number.

21000736 is a deficient number, since it is larger than the sum of its proper divisors (20344526).

21000736 is an equidigital number, since it uses as much as digits as its factorization.

21000736 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 656283 (or 656275 counting only the distinct ones).

The product of its (nonzero) digits is 252, while the sum is 19.

The square root of 21000736 is about 4582.6559984358. The cubic root of 21000736 is about 275.8956407246.

Adding to 21000736 its reverse (63700012), we get a palindrome (84700748).

It can be divided in two parts, 21000 and 736, that added together give a triangular number (21736 = T₂₀₈).

The spelling of 21000736 in words is "twenty-one million, seven hundred thirty-six", and thus it is an aban number.