21063640 has 32 divisors (see below), whose sum is σ = 51040080. Its totient is φ = 7777152.

The previous prime is 21063569. The next prime is 21063673. The reversal of 21063640 is 4636012.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19734 + ... + 20773.

Almost surely, 2^21063640 is an apocalyptic number.

21063640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21063640 is an abundant number, since it is smaller than the sum of its proper divisors (29976440).

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

21063640 is a wasteful number, since it uses less digits than its factorization.

21063640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40531 (or 40527 counting only the distinct ones).

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

The square root of 21063640 is about 4589.5141355050. The cubic root of 21063640 is about 276.1708317191.

Adding to 21063640 its reverse (4636012), we get a palindrome (25699652).

The spelling of 21063640 in words is "twenty-one million, sixty-three thousand, six hundred forty".