21917830 has 32 divisors (see below), whose sum is σ = 45308160. Its totient is φ = 7549920.

The previous prime is 21917813. The next prime is 21917843. The reversal of 21917830 is 3871912.

It is a junction number, because it is equal to n+sod(n) for n = 21917792 and 21917801.

It is a congruent number.

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 15 ways as a sum of consecutive naturals, for example, 3154 + ... + 7333.

It is an arithmetic number, because the mean of its divisors is an integer number (1415880).

Almost surely, 2^21917830 is an apocalyptic number.

21917830 is an abundant number, since it is smaller than the sum of its proper divisors (23390330).

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

21917830 is a wasteful number, since it uses less digits than its factorization.

21917830 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10524.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 21917830 is about 4681.6482140374. The cubic root of 21917830 is about 279.8546439423.

The spelling of 21917830 in words is "twenty-one million, nine hundred seventeen thousand, eight hundred thirty".