21643000 has 64 divisors (see below), whose sum is σ = 52902720. Its totient is φ = 8272000.

The previous prime is 21642979. The next prime is 21643009. The reversal of 21643000 is 34612.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21643009) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 22530 + ... + 23470.

It is an arithmetic number, because the mean of its divisors is an integer number (826605).

Almost surely, 2^21643000 is an apocalyptic number.

21643000 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 21643000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (26451360).

21643000 is an abundant number, since it is smaller than the sum of its proper divisors (31259720).

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

21643000 is a wasteful number, since it uses less digits than its factorization.

21643000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 985 (or 971 counting only the distinct ones).

The product of its (nonzero) digits is 144, while the sum is 16.

The square root of 21643000 is about 4652.2037788558. The cubic root of 21643000 is about 278.6800115198.

Adding to 21643000 its reverse (34612), we get a palindrome (21677612).

The spelling of 21643000 in words is "twenty-one million, six hundred forty-three thousand".