21431855 has 8 divisors (see below), whose sum is σ = 25743264. Its totient is φ = 17128800.

The previous prime is 21431821. The next prime is 21431863. The reversal of 21431855 is 55813412.

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

It is not a de Polignac number, because 21431855 - 2¹⁰ = 21430831 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7985 + ... + 10325.

It is an arithmetic number, because the mean of its divisors is an integer number (3217908).

Almost surely, 2^21431855 is an apocalyptic number.

21431855 is a deficient number, since it is larger than the sum of its proper divisors (4311409).

21431855 is a wasteful number, since it uses less digits than its factorization.

21431855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4177.

The product of its digits is 4800, while the sum is 29.

The square root of 21431855 is about 4629.4551515270. The cubic root of 21431855 is about 277.7707986098.

The spelling of 21431855 in words is "twenty-one million, four hundred thirty-one thousand, eight hundred fifty-five".