21897643 has 8 divisors (see below), whose sum is σ = 22176000. Its totient is φ = 21621288.

The previous prime is 21897637. The next prime is 21897647. The reversal of 21897643 is 34679812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21897643 - 2⁵ = 21897611 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21897596 and 21897605.

It is not an unprimeable number, because it can be changed into a prime (21897647) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 36258 + ... + 36856.

It is an arithmetic number, because the mean of its divisors is an integer number (2772000).

Almost surely, 2^21897643 is an apocalyptic number.

21897643 is a deficient number, since it is larger than the sum of its proper divisors (278357).

21897643 is a wasteful number, since it uses less digits than its factorization.

21897643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1001.

The product of its digits is 72576, while the sum is 40.

The square root of 21897643 is about 4679.4917459057. The cubic root of 21897643 is about 279.7686992872.

The spelling of 21897643 in words is "twenty-one million, eight hundred ninety-seven thousand, six hundred forty-three".