21208144 has 10 divisors (see below), whose sum is σ = 41090810. Its totient is φ = 10604064.

The previous prime is 21208133. The next prime is 21208151. The reversal of 21208144 is 44180212.

It can be written as a sum of positive squares in only one way, i.e., 19465744 + 1742400 = 4412^2 + 1320^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 662739 + ... + 662770.

It is an arithmetic number, because the mean of its divisors is an integer number (4109081).

Almost surely, 2^21208144 is an apocalyptic number.

It is an amenable number.

21208144 is a deficient number, since it is larger than the sum of its proper divisors (19882666).

21208144 is a wasteful number, since it uses less digits than its factorization.

21208144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1325517 (or 1325511 counting only the distinct ones).

The product of its (nonzero) digits is 512, while the sum is 22.

The square root of 21208144 is about 4605.2300702571. The cubic root of 21208144 is about 276.8009361012.

Adding to 21208144 its reverse (44180212), we get a palindrome (65388356).

The spelling of 21208144 in words is "twenty-one million, two hundred eight thousand, one hundred forty-four".