21717234 has 80 divisors (see below), whose sum is σ = 60705216. Its totient is φ = 5637600.

The previous prime is 21717217. The next prime is 21717253. The reversal of 21717234 is 43271712.

It is a happy number.

It is a super-2 number, since 2×21717234² = 943276505221512, which contains 22 as substring.

It is a hoax number, since the sum of its digits (27) coincides with the sum of the digits of its distinct prime factors.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a junction number, because it is equal to n+sod(n) for n = 21717198 and 21717207.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 11604 + ... + 13344.

Almost surely, 2^21717234 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21717234, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30352608).

21717234 is an abundant number, since it is smaller than the sum of its proper divisors (38987982).

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

21717234 is a wasteful number, since it uses less digits than its factorization.

21717234 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1773 (or 1764 counting only the distinct ones).

The product of its digits is 2352, while the sum is 27.

The square root of 21717234 is about 4660.1753185905. The cubic root of 21717234 is about 278.9982656847.

Adding to 21717234 its reverse (43271712), we get a palindrome (64988946).

The spelling of 21717234 in words is "twenty-one million, seven hundred seventeen thousand, two hundred thirty-four".