21755686 has 4 divisors (see below), whose sum is σ = 32633532. Its totient is φ = 10877842.

The previous prime is 21755683. The next prime is 21755717. The reversal of 21755686 is 68655712.

It is a semiprime because it is the product of two primes.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21755683) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5438920 + ... + 5438923.

It is an arithmetic number, because the mean of its divisors is an integer number (8158383).

Almost surely, 2^21755686 is an apocalyptic number.

21755686 is a deficient number, since it is larger than the sum of its proper divisors (10877846).

21755686 is a wasteful number, since it uses less digits than its factorization.

21755686 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10877845.

The product of its digits is 100800, while the sum is 40.

The square root of 21755686 is about 4664.2990898955. The cubic root of 21755686 is about 279.1628310851.

The spelling of 21755686 in words is "twenty-one million, seven hundred fifty-five thousand, six hundred eighty-six".