21663020 has 12 divisors (see below), whose sum is σ = 45492384. Its totient is φ = 8665200.

The previous prime is 21662989. The next prime is 21663041. The reversal of 21663020 is 2036612.

It is a Harshad number since it is a multiple of its sum of digits (20), and also a Moran number because the ratio is a prime number: 1083151 = 21663020 / (2 + 1 + 6 + 6 + 3 + 0 + 2 + 0).

It is a junction number, because it is equal to n+sod(n) for n = 21662983 and 21663001.

It is an unprimeable number.

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, 541556 + ... + 541595.

It is an arithmetic number, because the mean of its divisors is an integer number (3791032).

Almost surely, 2^21663020 is an apocalyptic number.

21663020 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21663020 is an abundant number, since it is smaller than the sum of its proper divisors (23829364).

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

21663020 is a wasteful number, since it uses less digits than its factorization.

21663020 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1083160 (or 1083158 counting only the distinct ones).

The product of its (nonzero) digits is 432, while the sum is 20.

The square root of 21663020 is about 4654.3549499367. The cubic root of 21663020 is about 278.7659123414.

Adding to 21663020 its reverse (2036612), we get a palindrome (23699632).

It can be divided in two parts, 216 and 63020, that added together give a palindrome (63236).

The spelling of 21663020 in words is "twenty-one million, six hundred sixty-three thousand, twenty".