21750231 has 16 divisors (see below), whose sum is σ = 30727040. Its totient is φ = 13646880.

The previous prime is 21750229. The next prime is 21750241. The reversal of 21750231 is 13205712.

It is not a de Polignac number, because 21750231 - 2¹ = 21750229 is a prime.

It is a super-2 number, since 2×21750231² = 946145097106722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21750198 and 21750207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21750241) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8121 + ... + 10461.

It is an arithmetic number, because the mean of its divisors is an integer number (1920440).

Almost surely, 2^21750231 is an apocalyptic number.

21750231 is a deficient number, since it is larger than the sum of its proper divisors (8976809).

21750231 is a wasteful number, since it uses less digits than its factorization.

21750231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2526.

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 21750231 is about 4663.7142922782. The cubic root of 21750231 is about 279.1394967939.

Adding to 21750231 its reverse (13205712), we get a palindrome (34955943).

The spelling of 21750231 in words is "twenty-one million, seven hundred fifty thousand, two hundred thirty-one".