21217000 has 96 divisors (see below), whose sum is σ = 57886920. Its totient is φ = 7257600.

The previous prime is 21216997. The next prime is 21217019. The reversal of 21217000 is 71212.

It can be written as a sum of positive squares in 4 ways, for example, as 2502724 + 18714276 = 1582^2 + 4326^2 .

It is a super-2 number, since 2×21217000² = 900322178000000, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 48784 + ... + 49216.

Almost surely, 2^21217000 is an apocalyptic number.

21217000 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 21217000, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28943460).

21217000 is an abundant number, since it is smaller than the sum of its proper divisors (36669920).

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

21217000 is a wasteful number, since it uses less digits than its factorization.

21217000 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 468 (or 447 counting only the distinct ones).

The product of its (nonzero) digits is 28, while the sum is 13.

The square root of 21217000 is about 4606.1914853814. The cubic root of 21217000 is about 276.8394591635.

Adding to 21217000 its reverse (71212), we get a palindrome (21288212).

The spelling of 21217000 in words is "twenty-one million, two hundred seventeen thousand".