21690235 has 16 divisors (see below), whose sum is σ = 30707712. Its totient is φ = 14392800.

The previous prime is 21690233. The next prime is 21690239. The reversal of 21690235 is 53209612.

It is not a de Polignac number, because 21690235 - 2¹ = 21690233 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21690233) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8911 + ... + 11080.

It is an arithmetic number, because the mean of its divisors is an integer number (1919232).

Almost surely, 2^21690235 is an apocalyptic number.

21690235 is a deficient number, since it is larger than the sum of its proper divisors (9017477).

21690235 is a wasteful number, since it uses less digits than its factorization.

21690235 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20034.

The product of its (nonzero) digits is 3240, while the sum is 28.

The square root of 21690235 is about 4657.2776382775. The cubic root of 21690235 is about 278.8826002814.

Adding to 21690235 its reverse (53209612), we get a palindrome (74899847).

The spelling of 21690235 in words is "twenty-one million, six hundred ninety thousand, two hundred thirty-five".