21686673 has 4 divisors (see below), whose sum is σ = 28915568. Its totient is φ = 14457780.

The previous prime is 21686671. The next prime is 21686741. The reversal of 21686673 is 37668612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21686673 - 2¹ = 21686671 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21686671) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3614443 + ... + 3614448.

It is an arithmetic number, because the mean of its divisors is an integer number (7228892).

Almost surely, 2^21686673 is an apocalyptic number.

It is an amenable number.

21686673 is a deficient number, since it is larger than the sum of its proper divisors (7228895).

21686673 is an equidigital number, since it uses as much as digits as its factorization.

21686673 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7228894.

The product of its digits is 72576, while the sum is 39.

The square root of 21686673 is about 4656.8952103306. The cubic root of 21686673 is about 278.8673332852.

The spelling of 21686673 in words is "twenty-one million, six hundred eighty-six thousand, six hundred seventy-three".