21509930 has 32 divisors (see below), whose sum is σ = 44153424. Its totient is φ = 7474176.

The previous prime is 21509923. The next prime is 21509941. The reversal of 21509930 is 3990512.

It can be written as a sum of positive squares in 8 ways, for example, as 12694969 + 8814961 = 3563^2 + 2969^2 .

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21509893 and 21509902.

It is an unprimeable number.

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 15 ways as a sum of consecutive naturals, for example, 2657 + ... + 7076.

Almost surely, 2^21509930 is an apocalyptic number.

21509930 is an abundant number, since it is smaller than the sum of its proper divisors (22643494).

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

21509930 is a wasteful number, since it uses less digits than its factorization.

21509930 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9770.

The product of its (nonzero) digits is 2430, while the sum is 29.

The square root of 21509930 is about 4637.8799035766. The cubic root of 21509930 is about 278.1076907967.

The spelling of 21509930 in words is "twenty-one million, five hundred nine thousand, nine hundred thirty".