21320144 has 10 divisors (see below), whose sum is σ = 41307810. Its totient is φ = 10660064.

The previous prime is 21320107. The next prime is 21320183. The reversal of 21320144 is 44102312.

It can be written as a sum of positive squares in only one way, i.e., 21049744 + 270400 = 4588^2 + 520^2 .

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, 666239 + ... + 666270.

It is an arithmetic number, because the mean of its divisors is an integer number (4130781).

Almost surely, 2^21320144 is an apocalyptic number.

It is an amenable number.

21320144 is a deficient number, since it is larger than the sum of its proper divisors (19987666).

21320144 is a wasteful number, since it uses less digits than its factorization.

21320144 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1332517 (or 1332511 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 17.

The square root of 21320144 is about 4617.3741455507. The cubic root of 21320144 is about 277.2873418762.

Adding to 21320144 its reverse (44102312), we get a palindrome (65422456).

The spelling of 21320144 in words is "twenty-one million, three hundred twenty thousand, one hundred forty-four".