21053823 has 16 divisors (see below), whose sum is σ = 32209920. Its totient is φ = 11982816.

The previous prime is 21053783. The next prime is 21053831. The reversal of 21053823 is 32835012.

It is not a de Polignac number, because 21053823 - 2⁸ = 21053567 is a prime.

It is a zygodrome in base 4.

It is a junction number, because it is equal to n+sod(n) for n = 21053793 and 21053802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21053833) 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, 3786 + ... + 7512.

It is an arithmetic number, because the mean of its divisors is an integer number (2013120).

Almost surely, 2^21053823 is an apocalyptic number.

21053823 is a deficient number, since it is larger than the sum of its proper divisors (11156097).

21053823 is a wasteful number, since it uses less digits than its factorization.

21053823 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4006.

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 21053823 is about 4588.4445076736. Note that the first 3 decimals coincide. The cubic root of 21053823 is about 276.1279206433.

Adding to 21053823 its reverse (32835012), we get a palindrome (53888835).

The spelling of 21053823 in words is "twenty-one million, fifty-three thousand, eight hundred twenty-three".