21107730 has 96 divisors (see below), whose sum is σ = 59984064. Its totient is φ = 4738944.

The previous prime is 21107729. The next prime is 21107753. The reversal of 21107730 is 3770112.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a junction number, because it is equal to n+sod(n) for n = 21107697 and 21107706.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 121924 + ... + 122096.

It is an arithmetic number, because the mean of its divisors is an integer number (624834).

Almost surely, 2^21107730 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21107730, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29992032).

21107730 is an abundant number, since it is smaller than the sum of its proper divisors (38876334).

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

21107730 is a wasteful number, since it uses less digits than its factorization.

21107730 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 280 (or 273 counting only the distinct ones).

The product of its (nonzero) digits is 294, while the sum is 21.

The square root of 21107730 is about 4594.3149652587. The cubic root of 21107730 is about 276.3633892266.

Adding to 21107730 its reverse (3770112), we get a palindrome (24877842).

The spelling of 21107730 in words is "twenty-one million, one hundred seven thousand, seven hundred thirty".