21320505 has 12 divisors (see below), whose sum is σ = 36955620. Its totient is φ = 11370912.

The previous prime is 21320491. The next prime is 21320513. The reversal of 21320505 is 50502312.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 12194064 + 9126441 = 3492^2 + 3021^2 .

It is not a de Polignac number, because 21320505 - 2¹⁰ = 21319481 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 236850 + ... + 236939.

It is an arithmetic number, because the mean of its divisors is an integer number (3079635).

Almost surely, 2^21320505 is an apocalyptic number.

It is an amenable number.

21320505 is a deficient number, since it is larger than the sum of its proper divisors (15635115).

21320505 is a wasteful number, since it uses less digits than its factorization.

21320505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 473800 (or 473797 counting only the distinct ones).

The product of its (nonzero) digits is 300, while the sum is 18.

The square root of 21320505 is about 4617.4132368676. The cubic root of 21320505 is about 277.2889069089.

Adding to 21320505 its reverse (50502312), we get a palindrome (71822817).

The spelling of 21320505 in words is "twenty-one million, three hundred twenty thousand, five hundred five".