21520144 has 10 divisors (see below), whose sum is σ = 41695310. Its totient is φ = 10760064.

The previous prime is 21520139. The next prime is 21520151. The reversal of 21520144 is 44102512.

It can be written as a sum of positive squares in only one way, i.e., 15210000 + 6310144 = 3900^2 + 2512^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 672489 + ... + 672520.

It is an arithmetic number, because the mean of its divisors is an integer number (4169531).

Almost surely, 2^21520144 is an apocalyptic number.

It is an amenable number.

21520144 is a deficient number, since it is larger than the sum of its proper divisors (20175166).

21520144 is a wasteful number, since it uses less digits than its factorization.

21520144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1345017 (or 1345011 counting only the distinct ones).

The product of its (nonzero) digits is 320, while the sum is 19.

The square root of 21520144 is about 4638.9809225734. The cubic root of 21520144 is about 278.1517036852.

Adding to 21520144 its reverse (44102512), we get a palindrome (65622656).

The spelling of 21520144 in words is "twenty-one million, five hundred twenty thousand, one hundred forty-four".