21821030 has 64 divisors (see below), whose sum is σ = 51881472. Its totient is φ = 6397440.

The previous prime is 21821027. The next prime is 21821039. The reversal of 21821030 is 3012812.

It is a Harshad number since it is a multiple of its sum of digits (17).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21821039) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 12257 + ... + 13923.

It is an arithmetic number, because the mean of its divisors is an integer number (810648).

Almost surely, 2^21821030 is an apocalyptic number.

21821030 is an abundant number, since it is smaller than the sum of its proper divisors (30060442).

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

21821030 is a wasteful number, since it uses less digits than its factorization.

21821030 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1709.

The product of its (nonzero) digits is 96, while the sum is 17.

The square root of 21821030 is about 4671.2985346689. The cubic root of 21821030 is about 279.4420436602.

Adding to 21821030 its reverse (3012812), we get a palindrome (24833842).

The spelling of 21821030 in words is "twenty-one million, eight hundred twenty-one thousand, thirty".