21680643 has 8 divisors (see below), whose sum is σ = 29579968. Its totient is φ = 14117544.

The previous prime is 21680641. The next prime is 21680669. The reversal of 21680643 is 34608612.

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

It is not a de Polignac number, because 21680643 - 2¹ = 21680641 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21680643.

It is not an unprimeable number, because it can be changed into a prime (21680641) 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, 83905 + ... + 84162.

It is an arithmetic number, because the mean of its divisors is an integer number (3697496).

Almost surely, 2^21680643 is an apocalyptic number.

21680643 is a deficient number, since it is larger than the sum of its proper divisors (7899325).

21680643 is a wasteful number, since it uses less digits than its factorization.

21680643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 168113.

The product of its (nonzero) digits is 6912, while the sum is 30.

The square root of 21680643 is about 4656.2477382545. The cubic root of 21680643 is about 278.8414844471.

The spelling of 21680643 in words is "twenty-one million, six hundred eighty thousand, six hundred forty-three".