21640364 has 12 divisors (see below), whose sum is σ = 38039064. Its totient is φ = 10772064.

The previous prime is 21640363. The next prime is 21640379. The reversal of 21640364 is 46304612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21640363) 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, 11009 + ... + 12824.

It is an arithmetic number, because the mean of its divisors is an integer number (3169922).

Almost surely, 2^21640364 is an apocalyptic number.

It is an amenable number.

21640364 is a deficient number, since it is larger than the sum of its proper divisors (16398700).

21640364 is a wasteful number, since it uses less digits than its factorization.

21640364 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 24064 (or 24062 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 26.

The square root of 21640364 is about 4651.9204636365. The cubic root of 21640364 is about 278.6686971559.

Adding to 21640364 its reverse (46304612), we get a palindrome (67944976).

The spelling of 21640364 in words is "twenty-one million, six hundred forty thousand, three hundred sixty-four".