21730100 has 72 divisors (see below), whose sum is σ = 55413120. Its totient is φ = 7240320.

The previous prime is 21730099. The next prime is 21730109. The reversal of 21730100 is 103712.

It is a Harshad number since it is a multiple of its sum of digits (14).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21730109) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 25481 + ... + 26319.

Almost surely, 2^21730100 is an apocalyptic number.

21730100 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 21730100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27706560).

21730100 is an abundant number, since it is smaller than the sum of its proper divisors (33683020).

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

21730100 is a wasteful number, since it uses less digits than its factorization.

21730100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 897 (or 890 counting only the distinct ones).

The product of its (nonzero) digits is 42, while the sum is 14.

The square root of 21730100 is about 4661.5555343683. Note that the first 4 decimals coincide. The cubic root of 21730100 is about 279.0533507085.

Adding to 21730100 its reverse (103712), we get a palindrome (21833812).

The spelling of 21730100 in words is "twenty-one million, seven hundred thirty thousand, one hundred".