21309242 has 8 divisors (see below), whose sum is σ = 32056500. Its totient is φ = 10623744.

The previous prime is 21309221. The next prime is 21309257. The reversal of 21309242 is 24290312.

It can be written as a sum of positive squares in 2 ways, for example, as 20079361 + 1229881 = 4481^2 + 1109^2 .

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

It is a super-2 number, since 2×21309242² = 908167589229128, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14567 + ... + 15962.

Almost surely, 2^21309242 is an apocalyptic number.

21309242 is a deficient number, since it is larger than the sum of its proper divisors (10747258).

21309242 is a wasteful number, since it uses less digits than its factorization.

21309242 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30880.

The product of its (nonzero) digits is 864, while the sum is 23.

The square root of 21309242 is about 4616.1934534852. The cubic root of 21309242 is about 277.2400704317.

Adding to 21309242 its reverse (24290312), we get a palindrome (45599554).

The spelling of 21309242 in words is "twenty-one million, three hundred nine thousand, two hundred forty-two".