21500505 has 32 divisors (see below), whose sum is σ = 41166720. Its totient is φ = 10584000.

The previous prime is 21500503. The next prime is 21500509. The reversal of 21500505 is 50500512.

It is not a de Polignac number, because 21500505 - 2¹ = 21500503 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21500503) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4371 + ... + 7880.

It is an arithmetic number, because the mean of its divisors is an integer number (1286460).

Almost surely, 2^21500505 is an apocalyptic number.

It is an amenable number.

21500505 is a deficient number, since it is larger than the sum of its proper divisors (19666215).

21500505 is a wasteful number, since it uses less digits than its factorization.

21500505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12278 (or 12272 counting only the distinct ones).

The product of its (nonzero) digits is 250, while the sum is 18.

The square root of 21500505 is about 4636.8637029786. The cubic root of 21500505 is about 278.0670654062.

The spelling of 21500505 in words is "twenty-one million, five hundred thousand, five hundred five".