21705000 has 80 divisors (see below), whose sum is σ = 67853280. Its totient is φ = 5784000.

The previous prime is 21704999. The next prime is 21705007. The reversal of 21705000 is 50712.

It is a happy number.

It is a super-2 number, since 2×21705000² = 942214050000000, which contains 22 as substring.

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

It is not an unprimeable number, because it can be changed into a prime (21705007) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 14277 + ... + 15723.

It is an arithmetic number, because the mean of its divisors is an integer number (848166).

Almost surely, 2^21705000 is an apocalyptic number.

21705000 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 21705000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33926640).

21705000 is an abundant number, since it is smaller than the sum of its proper divisors (46148280).

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

21705000 is a wasteful number, since it uses less digits than its factorization.

21705000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1476 (or 1457 counting only the distinct ones).

The product of its (nonzero) digits is 70, while the sum is 15.

The square root of 21705000 is about 4658.8625221185. The cubic root of 21705000 is about 278.9458663488.

Adding to 21705000 its reverse (50712), we get a palindrome (21755712).

The spelling of 21705000 in words is "twenty-one million, seven hundred five thousand".