21851000 has 32 divisors (see below), whose sum is σ = 51133680. Its totient is φ = 8740000.

The previous prime is 21850987. The next prime is 21851003. The reversal of 21851000 is 15812.

21851000 is nontrivially palindromic in base 7.

It is a self number, because there is not a number n which added to its sum of digits gives 21851000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21851003) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9926 + ... + 11925.

Almost surely, 2^21851000 is an apocalyptic number.

21851000 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21851000 is an abundant number, since it is smaller than the sum of its proper divisors (29282680).

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

21851000 is a wasteful number, since it uses less digits than its factorization.

21851000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21872 (or 21858 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 17.

The square root of 21851000 is about 4674.5053214217. The cubic root of 21851000 is about 279.5699179604.

Adding to 21851000 its reverse (15812), we get a palindrome (21866812).

The spelling of 21851000 in words is "twenty-one million, eight hundred fifty-one thousand".