21630320 has 20 divisors (see below), whose sum is σ = 50290680. Its totient is φ = 8652096.

The previous prime is 21630289. The next prime is 21630337. The reversal of 21630320 is 2303612.

It is a tau number, because it is divible by the number of its divisors (20).

It is a congruent number.

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, 135110 + ... + 135269.

It is an arithmetic number, because the mean of its divisors is an integer number (2514534).

Almost surely, 2^21630320 is an apocalyptic number.

21630320 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21630320 is an abundant number, since it is smaller than the sum of its proper divisors (28660360).

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

21630320 is a wasteful number, since it uses less digits than its factorization.

21630320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 270392 (or 270386 counting only the distinct ones).

The product of its (nonzero) digits is 216, while the sum is 17.

The square root of 21630320 is about 4650.8407842024. The cubic root of 21630320 is about 278.6255774016.

Adding to 21630320 its reverse (2303612), we get a palindrome (23933932).

The spelling of 21630320 in words is "twenty-one million, six hundred thirty thousand, three hundred twenty".