21698820 has 192 divisors, whose sum is σ = 79591680. Its totient is φ = 4838400.

The previous prime is 21698801. The next prime is 21698827. The reversal of 21698820 is 2889612.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (21698827) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 77080 + ... + 77360.

It is an arithmetic number, because the mean of its divisors is an integer number (414540).

Almost surely, 2^21698820 is an apocalyptic number.

21698820 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21698820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (39795840).

21698820 is an abundant number, since it is smaller than the sum of its proper divisors (57892860).

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

21698820 is a wasteful number, since it uses less digits than its factorization.

21698820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 323 (or 315 counting only the distinct ones).

The product of its (nonzero) digits is 13824, while the sum is 36.

The square root of 21698820 is about 4658.1992228757. The cubic root of 21698820 is about 278.9193893605.

The spelling of 21698820 in words is "twenty-one million, six hundred ninety-eight thousand, eight hundred twenty".