21406530 has 32 divisors (see below), whose sum is σ = 52000704. Its totient is φ = 5638976.

The previous prime is 21406529. The next prime is 21406531. The reversal of 21406530 is 3560412.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21406529) and next prime (21406531).

It is a junction number, because it is equal to n+sod(n) for n = 21406497 and 21406506.

It is not an unprimeable number, because it can be changed into a prime (21406531) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1809 + ... + 6788.

It is an arithmetic number, because the mean of its divisors is an integer number (1625022).

Almost surely, 2^21406530 is an apocalyptic number.

21406530 is an abundant number, since it is smaller than the sum of its proper divisors (30594174).

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

21406530 is a wasteful number, since it uses less digits than its factorization.

21406530 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8690.

The product of its (nonzero) digits is 720, while the sum is 21.

The square root of 21406530 is about 4626.7191399522. The cubic root of 21406530 is about 277.6613459891.

Adding to 21406530 its reverse (3560412), we get a palindrome (24966942).

The spelling of 21406530 in words is "twenty-one million, four hundred six thousand, five hundred thirty".