21455687 has 4 divisors (see below), whose sum is σ = 23406216. Its totient is φ = 19505160.

The previous prime is 21455677. The next prime is 21455699. The reversal of 21455687 is 78655412.

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 21455687 - 2⁸ = 21455431 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 21455687.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21455677) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 975248 + ... + 975269.

It is an arithmetic number, because the mean of its divisors is an integer number (5851554).

Almost surely, 2^21455687 is an apocalyptic number.

21455687 is a deficient number, since it is larger than the sum of its proper divisors (1950529).

21455687 is a wasteful number, since it uses less digits than its factorization.

21455687 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1950528.

The product of its digits is 67200, while the sum is 38.

The square root of 21455687 is about 4632.0283893776. The cubic root of 21455687 is about 277.8737198838.

The spelling of 21455687 in words is "twenty-one million, four hundred fifty-five thousand, six hundred eighty-seven".