21755687 has 4 divisors (see below), whose sum is σ = 21850920. Its totient is φ = 21660456.

The previous prime is 21755683. The next prime is 21755717. The reversal of 21755687 is 78655712.

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

It is a cyclic number.

It is not a de Polignac number, because 21755687 - 2² = 21755683 is a prime.

It is a Duffinian 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 in 3 ways as a sum of consecutive naturals, for example, 47273 + ... + 47730.

It is an arithmetic number, because the mean of its divisors is an integer number (5462730).

Almost surely, 2^21755687 is an apocalyptic number.

21755687 is a deficient number, since it is larger than the sum of its proper divisors (95233).

21755687 is an equidigital number, since it uses as much as digits as its factorization.

21755687 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95232.

The product of its digits is 117600, while the sum is 41.

The square root of 21755687 is about 4664.2991970927. The cubic root of 21755687 is about 279.1628353624.

The spelling of 21755687 in words is "twenty-one million, seven hundred fifty-five thousand, six hundred eighty-seven".