21820104 has 80 divisors (see below), whose sum is σ = 61797120. Its totient is φ = 7192800.

The previous prime is 21820103. The next prime is 21820111. The reversal of 21820104 is 40102812.

It is a super-2 number, since 2×21820104² = 952233877141632, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is not an unprimeable number, because it can be changed into a prime (21820103) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 97737 + ... + 97959.

It is an arithmetic number, because the mean of its divisors is an integer number (772464).

Almost surely, 2^21820104 is an apocalyptic number.

21820104 is a gapful number since it is divisible by the number (24) 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 21820104, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30898560).

21820104 is an abundant number, since it is smaller than the sum of its proper divisors (39977016).

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

21820104 is a wasteful number, since it uses less digits than its factorization.

21820104 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 392 (or 379 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 18.

The square root of 21820104 is about 4671.1994177085. The cubic root of 21820104 is about 279.4380907916.

Adding to 21820104 its reverse (40102812), we get a palindrome (61922916).

The spelling of 21820104 in words is "twenty-one million, eight hundred twenty thousand, one hundred four".