21661123 has 8 divisors (see below), whose sum is σ = 23718960. Its totient is φ = 19618080.

The previous prime is 21661109. The next prime is 21661141. The reversal of 21661123 is 32116612.

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 21661123 - 2¹³ = 21652931 is a prime.

It is a super-2 number, since 2×21661123² = 938408499242258, 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 = 21661094 and 21661103.

It is not an unprimeable number, because it can be changed into a prime (21661183) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 508 + ... + 6601.

It is an arithmetic number, because the mean of its divisors is an integer number (2964870).

Almost surely, 2^21661123 is an apocalyptic number.

21661123 is a deficient number, since it is larger than the sum of its proper divisors (2057837).

21661123 is a wasteful number, since it uses less digits than its factorization.

21661123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7397.

The product of its digits is 432, while the sum is 22.

The square root of 21661123 is about 4654.1511578375. The cubic root of 21661123 is about 278.7577750585.

Adding to 21661123 its reverse (32116612), we get a palindrome (53777735).

The spelling of 21661123 in words is "twenty-one million, six hundred sixty-one thousand, one hundred twenty-three".