21645030 has 64 divisors (see below), whose sum is σ = 57293568. Its totient is φ = 5189760.

The previous prime is 21645023. The next prime is 21645053. The reversal of 21645030 is 3054612.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21644988 and 21645006.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 35004 + ... + 35616.

It is an arithmetic number, because the mean of its divisors is an integer number (895212).

Almost surely, 2^21645030 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21645030, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28646784).

21645030 is an abundant number, since it is smaller than the sum of its proper divisors (35648538).

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

21645030 is a wasteful number, since it uses less digits than its factorization.

21645030 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 741.

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21645030 is about 4652.4219499095. The cubic root of 21645030 is about 278.6887241557.

Adding to 21645030 its reverse (3054612), we get a palindrome (24699642).

The spelling of 21645030 in words is "twenty-one million, six hundred forty-five thousand, thirty".