21239730 has 24 divisors (see below), whose sum is σ = 55223532. Its totient is φ = 5663904.

The previous prime is 21239717. The next prime is 21239731. The reversal of 21239730 is 3793212.

It can be written as a sum of positive squares in 2 ways, for example, as 17114769 + 4124961 = 4137^2 + 2031^2 .

It is a super-2 number, since 2×21239730² = 902252260945800, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21239694 and 21239703.

It is not an unprimeable number, because it can be changed into a prime (21239731) by changing a digit.

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 11 ways as a sum of consecutive naturals, for example, 117909 + ... + 118088.

Almost surely, 2^21239730 is an apocalyptic number.

21239730 is an abundant number, since it is smaller than the sum of its proper divisors (33983802).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21239730 is a wasteful number, since it uses less digits than its factorization.

21239730 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 236010 (or 236007 counting only the distinct ones).

The product of its (nonzero) digits is 2268, while the sum is 27.

The square root of 21239730 is about 4608.6581561231. The cubic root of 21239730 is about 276.9382842432.

The spelling of 21239730 in words is "twenty-one million, two hundred thirty-nine thousand, seven hundred thirty".