21523420 has 12 divisors (see below), whose sum is σ = 45199224. Its totient is φ = 8609360.

The previous prime is 21523417. The next prime is 21523421. The reversal of 21523420 is 2432512.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523421) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 538066 + ... + 538105.

It is an arithmetic number, because the mean of its divisors is an integer number (3766602).

Almost surely, 2^21523420 is an apocalyptic number.

21523420 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21523420 is an abundant number, since it is smaller than the sum of its proper divisors (23675804).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21523420 is a wasteful number, since it uses less digits than its factorization.

21523420 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1076180 (or 1076178 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 19.

The square root of 21523420 is about 4639.3340039277. The cubic root of 21523420 is about 278.1658172641.

Adding to 21523420 its reverse (2432512), we get a palindrome (23955932).

The spelling of 21523420 in words is "twenty-one million, five hundred twenty-three thousand, four hundred twenty".