21554240 has 56 divisors (see below), whose sum is σ = 51739800. Its totient is φ = 8552448.

The previous prime is 21554237. The next prime is 21554257. The reversal of 21554240 is 4245512.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 1982464 + 19571776 = 1408^2 + 4424^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 61586 + ... + 61934.

It is an arithmetic number, because the mean of its divisors is an integer number (923925).

Almost surely, 2^21554240 is an apocalyptic number.

21554240 is a gapful number since it is divisible by the number (20) 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 21554240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25869900).

21554240 is an abundant number, since it is smaller than the sum of its proper divisors (30185560).

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

21554240 is a wasteful number, since it uses less digits than its factorization.

21554240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 559 (or 549 counting only the distinct ones).

The product of its (nonzero) digits is 1600, while the sum is 23.

The square root of 21554240 is about 4642.6544131563. The cubic root of 21554240 is about 278.2985251350.

Adding to 21554240 its reverse (4245512), we get a palindrome (25799752).

The spelling of 21554240 in words is "twenty-one million, five hundred fifty-four thousand, two hundred forty".