21023861 has 8 divisors (see below), whose sum is σ = 22645920. Its totient is φ = 19453392.

The previous prime is 21023851. The next prime is 21023867. The reversal of 21023861 is 16832012.

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 21023861 - 2¹⁸ = 20761717 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21023867) 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, 12050 + ... + 13683.

It is an arithmetic number, because the mean of its divisors is an integer number (2830740).

Almost surely, 2^21023861 is an apocalyptic number.

It is an amenable number.

21023861 is a deficient number, since it is larger than the sum of its proper divisors (1622059).

21023861 is a wasteful number, since it uses less digits than its factorization.

21023861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25795.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21023861 is about 4585.1784043808. The cubic root of 21023861 is about 275.9968712451.

Adding to 21023861 its reverse (16832012), we get a palindrome (37855873).

The spelling of 21023861 in words is "twenty-one million, twenty-three thousand, eight hundred sixty-one".