21001830 has 32 divisors (see below), whose sum is σ = 50588928. Its totient is φ = 5580000.

The previous prime is 21001823. The next prime is 21001831. The reversal of 21001830 is 3810012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8205 + ... + 10455.

It is an arithmetic number, because the mean of its divisors is an integer number (1580904).

Almost surely, 2^21001830 is an apocalyptic number.

21001830 is an abundant number, since it is smaller than the sum of its proper divisors (29587098).

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

21001830 is a wasteful number, since it uses less digits than its factorization.

21001830 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2572.

The product of its (nonzero) digits is 48, while the sum is 15.

The square root of 21001830 is about 4582.7753599757. The cubic root of 21001830 is about 275.9004314232.

Adding to 21001830 its reverse (3810012), we get a palindrome (24811842).

The spelling of 21001830 in words is "twenty-one million, one thousand, eight hundred thirty".