21403564 has 48 divisors (see below), whose sum is σ = 46563328. Its totient is φ = 8382528.

The previous prime is 21403559. The next prime is 21403579. The reversal of 21403564 is 46530412.

It is a super-2 number, since 2×21403564² = 916225103804192, which contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 45997 + ... + 46459.

Almost surely, 2^21403564 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21403564, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23281664).

21403564 is an abundant number, since it is smaller than the sum of its proper divisors (25159764).

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

21403564 is a wasteful number, since it uses less digits than its factorization.

21403564 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 614 (or 612 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 25.

The square root of 21403564 is about 4626.3985993427. The cubic root of 21403564 is about 277.6485215287.

Adding to 21403564 its reverse (46530412), we get a palindrome (67933976).

The spelling of 21403564 in words is "twenty-one million, four hundred three thousand, five hundred sixty-four".