21287138 has 8 divisors (see below), whose sum is σ = 31950288. Its totient is φ = 10637044.

The previous prime is 21287137. The next prime is 21287143. The reversal of 21287138 is 83178212.

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

It is not an unprimeable number, because it can be changed into a prime (21287137) 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, 4745 + ... + 8067.

It is an arithmetic number, because the mean of its divisors is an integer number (3993786).

Almost surely, 2^21287138 is an apocalyptic number.

21287138 is a deficient number, since it is larger than the sum of its proper divisors (10663150).

21287138 is a wasteful number, since it uses less digits than its factorization.

21287138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6528.

The product of its digits is 5376, while the sum is 32.

The square root of 21287138 is about 4613.7986518703. The cubic root of 21287138 is about 277.1441772252.

The spelling of 21287138 in words is "twenty-one million, two hundred eighty-seven thousand, one hundred thirty-eight".