21211723 has 8 divisors (see below), whose sum is σ = 22882608. Its totient is φ = 19546464.

The previous prime is 21211721. The next prime is 21211769. The reversal of 21211723 is 32711212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21211723 - 2¹ = 21211721 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21211723.

It is not an unprimeable number, because it can be changed into a prime (21211721) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9765 + ... + 11737.

It is an arithmetic number, because the mean of its divisors is an integer number (2860326).

Almost surely, 2^21211723 is an apocalyptic number.

21211723 is a deficient number, since it is larger than the sum of its proper divisors (1670885).

21211723 is a wasteful number, since it uses less digits than its factorization.

21211723 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2813.

The product of its digits is 168, while the sum is 19.

The square root of 21211723 is about 4605.6186337994. The cubic root of 21211723 is about 276.8165058249.

Adding to 21211723 its reverse (32711212), we get a palindrome (53922935).

It can be divided in two parts, 2121 and 1723, that added together give a square (3844 = 62²).

The spelling of 21211723 in words is "twenty-one million, two hundred eleven thousand, seven hundred twenty-three".