21523416 has 24 divisors (see below), whose sum is σ = 53865420. Its totient is φ = 7166896.

The previous prime is 21523399. The next prime is 21523417. The reversal of 21523416 is 61432512.

It is a tau number, because it is divible by the number of its divisors (24).

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523417) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 22255 + ... + 23201.

Almost surely, 2^21523416 is an apocalyptic number.

It is an amenable number.

21523416 is an abundant number, since it is smaller than the sum of its proper divisors (32342004).

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

21523416 is an frugal number, since it uses more digits than its factorization.

21523416 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1903 (or 952 counting only the distinct ones).

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

The square root of 21523416 is about 4639.3335728313. Note that the first 3 decimals coincide. The cubic root of 21523416 is about 278.1658000322.

Multiplying 21523416 by its sum of digits (24), we get a square (516561984 = 22728²).

21523416 divided by its sum of digits (24) gives a square (896809 = 947²).

Adding to 21523416 its reverse (61432512), we get a palindrome (82955928).

The spelling of 21523416 in words is "twenty-one million, five hundred twenty-three thousand, four hundred sixteen".