21217023 has 12 divisors (see below), whose sum is σ = 30686760. Its totient is φ = 14126256.

The previous prime is 21217019. The next prime is 21217033. The reversal of 21217023 is 32071212.

It is not a de Polignac number, because 21217023 - 2² = 21217019 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21216987 and 21217005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21217033) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 12648 + ... + 14226.

It is an arithmetic number, because the mean of its divisors is an integer number (2557230).

Almost surely, 2^21217023 is an apocalyptic number.

21217023 is a deficient number, since it is larger than the sum of its proper divisors (9469737).

21217023 is a wasteful number, since it uses less digits than its factorization.

21217023 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3078 (or 3075 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 18.

The square root of 21217023 is about 4606.1939820203. The cubic root of 21217023 is about 276.8395591982.

Adding to 21217023 its reverse (32071212), we get a palindrome (53288235).

The spelling of 21217023 in words is "twenty-one million, two hundred seventeen thousand, twenty-three".