21663830 has 32 divisors (see below), whose sum is σ = 40449024. Its totient is φ = 8348256.

The previous prime is 21663821. The next prime is 21663869. The reversal of 21663830 is 3836612.

It is a junction number, because it is equal to n+sod(n) for n = 21663793 and 21663802.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 35387 + ... + 35993.

It is an arithmetic number, because the mean of its divisors is an integer number (1264032).

Almost surely, 2^21663830 is an apocalyptic number.

21663830 is a deficient number, since it is larger than the sum of its proper divisors (18785194).

21663830 is a wasteful number, since it uses less digits than its factorization.

21663830 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 740.

The product of its (nonzero) digits is 5184, while the sum is 29.

The square root of 21663830 is about 4654.4419644035. The cubic root of 21663830 is about 278.7693867351.

It can be divided in two parts, 216 and 63830, that added together give a palindrome (64046).

The spelling of 21663830 in words is "twenty-one million, six hundred sixty-three thousand, eight hundred thirty".