21245544 has 64 divisors (see below), whose sum is σ = 60480000. Its totient is φ = 6906240.

The previous prime is 21245533. The next prime is 21245557. The reversal of 21245544 is 44554212.

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

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, 7657 + ... + 10055.

It is an arithmetic number, because the mean of its divisors is an integer number (945000).

Almost surely, 2^21245544 is an apocalyptic number.

21245544 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 21245544, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30240000).

21245544 is an abundant number, since it is smaller than the sum of its proper divisors (39234456).

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

21245544 is a wasteful number, since it uses less digits than its factorization.

21245544 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2455 (or 2445 counting only the distinct ones).

The product of its digits is 6400, while the sum is 27.

The square root of 21245544 is about 4609.2888822464. The cubic root of 21245544 is about 276.9635509218.

Adding to 21245544 its reverse (44554212), we get a palindrome (65799756).

The spelling of 21245544 in words is "twenty-one million, two hundred forty-five thousand, five hundred forty-four".