21390530 has 32 divisors (see below), whose sum is σ = 44167680. Its totient is φ = 7306560.

The previous prime is 21390517. The next prime is 21390541. The reversal of 21390530 is 3509312.

It is a happy number.

It is a zygodrome in base 9.

It is a junction number, because it is equal to n+sod(n) for n = 21390496 and 21390505.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29816 + ... + 30524.

It is an arithmetic number, because the mean of its divisors is an integer number (1380240).

Almost surely, 2^21390530 is an apocalyptic number.

21390530 is an abundant number, since it is smaller than the sum of its proper divisors (22777150).

21390530 is a wasteful number, since it uses less digits than its factorization.

21390530 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1154.

The product of its (nonzero) digits is 810, while the sum is 23.

The square root of 21390530 is about 4624.9897297183. The cubic root of 21390530 is about 277.5921507662.

Adding to 21390530 its reverse (3509312), we get a palindrome (24899842).

The spelling of 21390530 in words is "twenty-one million, three hundred ninety thousand, five hundred thirty".