21993828 has 12 divisors (see below), whose sum is σ = 51318960. Its totient is φ = 7331272.

The previous prime is 21993823. The next prime is 21993833. The reversal of 21993828 is 82839912.

It is an interprime number because it is at equal distance from previous prime (21993823) and next prime (21993833).

It is a tau number, because it is divible by the number of its divisors (12).

It is a self number, because there is not a number n which added to its sum of digits gives 21993828.

It is not an unprimeable number, because it can be changed into a prime (21993823) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 916398 + ... + 916421.

It is an arithmetic number, because the mean of its divisors is an integer number (4276580).

Almost surely, 2^21993828 is an apocalyptic number.

It is an amenable number.

21993828 is an abundant number, since it is smaller than the sum of its proper divisors (29325132).

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

21993828 is a wasteful number, since it uses less digits than its factorization.

21993828 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1832826 (or 1832824 counting only the distinct ones).

The product of its digits is 62208, while the sum is 42.

The square root of 21993828 is about 4689.7577762609. The cubic root of 21993828 is about 280.1777273015.

The spelling of 21993828 in words is "twenty-one million, nine hundred ninety-three thousand, eight hundred twenty-eight".