21213538 has 8 divisors (see below), whose sum is σ = 33495120. Its totient is φ = 10048500.

The previous prime is 21213487. The next prime is 21213553. The reversal of 21213538 is 83531212.

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

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 279088 + ... + 279163.

It is an arithmetic number, because the mean of its divisors is an integer number (4186890).

Almost surely, 2^21213538 is an apocalyptic number.

21213538 is a deficient number, since it is larger than the sum of its proper divisors (12281582).

21213538 is a wasteful number, since it uses less digits than its factorization.

21213538 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 558272.

The product of its digits is 1440, while the sum is 25.

The square root of 21213538 is about 4605.8156715179. The cubic root of 21213538 is about 276.8244009501.

The spelling of 21213538 in words is "twenty-one million, two hundred thirteen thousand, five hundred thirty-eight".