21663140 has 24 divisors (see below), whose sum is σ = 45729600. Its totient is φ = 8620128.

The previous prime is 21663139. The next prime is 21663149. The reversal of 21663140 is 4136612.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21663149) 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 7 ways as a sum of consecutive naturals, for example, 1259 + ... + 6701.

It is an arithmetic number, because the mean of its divisors is an integer number (1905400).

Almost surely, 2^21663140 is an apocalyptic number.

21663140 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21663140 is an abundant number, since it is smaller than the sum of its proper divisors (24066460).

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

21663140 is a wasteful number, since it uses less digits than its factorization.

21663140 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5651 (or 5649 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 23.

The square root of 21663140 is about 4654.3678410714. The cubic root of 21663140 is about 278.7664270719.

Adding to 21663140 its reverse (4136612), we get a palindrome (25799752).

The spelling of 21663140 in words is "twenty-one million, six hundred sixty-three thousand, one hundred forty".