21897216 has 168 divisors, whose sum is σ = 71560944. Its totient is φ = 6635520.

The previous prime is 21897193. The next prime is 21897223. The reversal of 21897216 is 61279812.

It is a Harshad number since it is a multiple of its sum of digits (36).

Its product of digits (12096) is a multiple of the sum of its prime divisors (16).

It is a nialpdrome in base 12.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1990651 + ... + 1990661.

It is an arithmetic number, because the mean of its divisors is an integer number (425958).

Almost surely, 2^21897216 is an apocalyptic number.

21897216 is a droll number since its even prime factors and its odd prime factors have the same sum.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21897216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35780472).

21897216 is an abundant number, since it is smaller than the sum of its proper divisors (49663728).

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

21897216 is an frugal number, since it uses more digits than its factorization.

21897216 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52 (or 16 counting only the distinct ones).

The product of its digits is 12096, while the sum is 36.

The square root of 21897216 is about 4679.4461210703. The cubic root of 21897216 is about 279.7668807961.

The spelling of 21897216 in words is "twenty-one million, eight hundred ninety-seven thousand, two hundred sixteen".