21321456 has 80 divisors (see below), whose sum is σ = 60662784. Its totient is φ = 6412032.

The previous prime is 21321449. The next prime is 21321481. The reversal of 21321456 is 65412312.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 28965 + ... + 29691.

Almost surely, 2^21321456 is an apocalyptic number.

21321456 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21321456, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30331392).

21321456 is an abundant number, since it is smaller than the sum of its proper divisors (39341328).

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

21321456 is a wasteful number, since it uses less digits than its factorization.

21321456 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 798 (or 792 counting only the distinct ones).

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

The square root of 21321456 is about 4617.5162154561. The cubic root of 21321456 is about 277.2930296666.

Adding to 21321456 its reverse (65412312), we get a palindrome (86733768).

It can be divided in two parts, 21 and 321456, that multiplied together give a palindrome (6750576).

The spelling of 21321456 in words is "twenty-one million, three hundred twenty-one thousand, four hundred fifty-six".