20681643 has 8 divisors (see below), whose sum is σ = 27596800. Its totient is φ = 13777128.

The previous prime is 20681641. The next prime is 20681653. The reversal of 20681643 is 34618602.

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

It is not a de Polignac number, because 20681643 - 2¹ = 20681641 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 20681643.

It is not an unprimeable number, because it can be changed into a prime (20681641) 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, 5178 + ... + 8256.

It is an arithmetic number, because the mean of its divisors is an integer number (3449600).

Almost surely, 2^20681643 is an apocalyptic number.

20681643 is a deficient number, since it is larger than the sum of its proper divisors (6915157).

20681643 is a wasteful number, since it uses less digits than its factorization.

20681643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5321.

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

The square root of 20681643 is about 4547.7074444164. The cubic root of 20681643 is about 274.4911493790.

The spelling of 20681643 in words is "twenty million, six hundred eighty-one thousand, six hundred forty-three".