21712216 has 8 divisors (see below), whose sum is σ = 40710420. Its totient is φ = 10856104.

The previous prime is 21712211. The next prime is 21712237. The reversal of 21712216 is 61221712.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (8).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21712211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1357006 + ... + 1357021.

Almost surely, 2^21712216 is an apocalyptic number.

It is an amenable number.

21712216 is a deficient number, since it is larger than the sum of its proper divisors (18998204).

21712216 is a wasteful number, since it uses less digits than its factorization.

21712216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2714033 (or 2714029 counting only the distinct ones).

The product of its digits is 336, while the sum is 22.

The square root of 21712216 is about 4659.6368957248. The cubic root of 21712216 is about 278.9767755148.

Adding to 21712216 its reverse (61221712), we get a palindrome (82933928).

The spelling of 21712216 in words is "twenty-one million, seven hundred twelve thousand, two hundred sixteen".