21431518 has 4 divisors (see below), whose sum is σ = 32147280. Its totient is φ = 10715758.

The previous prime is 21431507. The next prime is 21431521. The reversal of 21431518 is 81513412.

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

It is a junction number, because it is equal to n+sod(n) for n = 21431492 and 21431501.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5357878 + ... + 5357881.

It is an arithmetic number, because the mean of its divisors is an integer number (8036820).

Almost surely, 2^21431518 is an apocalyptic number.

21431518 is a deficient number, since it is larger than the sum of its proper divisors (10715762).

21431518 is a wasteful number, since it uses less digits than its factorization.

21431518 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10715761.

The product of its digits is 960, while the sum is 25.

The square root of 21431518 is about 4629.4187540122. The cubic root of 21431518 is about 277.7693426890.

The spelling of 21431518 in words is "twenty-one million, four hundred thirty-one thousand, five hundred eighteen".