21036640 has 24 divisors (see below), whose sum is σ = 49699440. Its totient is φ = 8414592.

The previous prime is 21036637. The next prime is 21036647. The reversal of 21036640 is 4663012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21036647) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 65580 + ... + 65899.

It is an arithmetic number, because the mean of its divisors is an integer number (2070810).

Almost surely, 2^21036640 is an apocalyptic number.

21036640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21036640 is an abundant number, since it is smaller than the sum of its proper divisors (28662800).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21036640 is a wasteful number, since it uses less digits than its factorization.

21036640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 131494 (or 131486 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 22.

The square root of 21036640 is about 4586.5717044433. The cubic root of 21036640 is about 276.0527799363.

Adding to 21036640 its reverse (4663012), we get a palindrome (25699652).

The spelling of 21036640 in words is "twenty-one million, thirty-six thousand, six hundred forty".