21798505 has 16 divisors (see below), whose sum is σ = 27818640. Its totient is φ = 16340992.

The previous prime is 21798499. The next prime is 21798509. The reversal of 21798505 is 50589712.

It can be written as a sum of positive squares in 8 ways, for example, as 8281 + 21790224 = 91^2 + 4668^2 .

It is a cyclic number.

It is not a de Polignac number, because 21798505 - 2¹⁷ = 21667433 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21798509) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 26541 + ... + 27349.

It is an arithmetic number, because the mean of its divisors is an integer number (1738665).

Almost surely, 2^21798505 is an apocalyptic number.

It is an amenable number.

21798505 is a deficient number, since it is larger than the sum of its proper divisors (6020135).

21798505 is a wasteful number, since it uses less digits than its factorization.

21798505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1148.

The product of its (nonzero) digits is 25200, while the sum is 37.

The square root of 21798505 is about 4668.8869123165. The cubic root of 21798505 is about 279.3458581744.

The spelling of 21798505 in words is "twenty-one million, seven hundred ninety-eight thousand, five hundred five".