21288431 has 8 divisors (see below), whose sum is σ = 21929040. Its totient is φ = 20651328.

The previous prime is 21288419. The next prime is 21288461. The reversal of 21288431 is 13488212.

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

It is not a de Polignac number, because 21288431 - 2¹⁰ = 21287407 is a prime.

It is a super-2 number, since 2×21288431² = 906394588883522, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21288394 and 21288403.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21288461) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16280 + ... + 17538.

It is an arithmetic number, because the mean of its divisors is an integer number (2741130).

Almost surely, 2^21288431 is an apocalyptic number.

21288431 is a deficient number, since it is larger than the sum of its proper divisors (640609).

21288431 is a wasteful number, since it uses less digits than its factorization.

21288431 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1753.

The product of its digits is 3072, while the sum is 29.

The square root of 21288431 is about 4613.9387728924. The cubic root of 21288431 is about 277.1497884409.

The spelling of 21288431 in words is "twenty-one million, two hundred eighty-eight thousand, four hundred thirty-one".