21390264 has 192 divisors, whose sum is σ = 72230400. Its totient is φ = 5842368.

The previous prime is 21390251. The next prime is 21390283. The reversal of 21390264 is 46209312.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 455089 + ... + 455135.

It is an arithmetic number, because the mean of its divisors is an integer number (376200).

Almost surely, 2^21390264 is an apocalyptic number.

21390264 is a gapful number since it is divisible by the number (24) 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 21390264, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (36115200).

21390264 is an abundant number, since it is smaller than the sum of its proper divisors (50840136).

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

21390264 is a wasteful number, since it uses less digits than its factorization.

21390264 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 119 (or 102 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 27.

The square root of 21390264 is about 4624.9609728083. The cubic root of 21390264 is about 277.5910001041.

Adding to 21390264 its reverse (46209312), we get a palindrome (67599576).

The spelling of 21390264 in words is "twenty-one million, three hundred ninety thousand, two hundred sixty-four".