21081384 has 40 divisors (see below), whose sum is σ = 59049210. Its totient is φ = 7026912.

The previous prime is 21081373. The next prime is 21081397. The reversal of 21081384 is 48318012.

It can be written as a sum of positive squares in only one way, i.e., 19448100 + 1633284 = 4410^2 + 1278^2 .

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 9 ways as a sum of consecutive naturals, for example, 15619 + ... + 16914.

Almost surely, 2^21081384 is an apocalyptic number.

21081384 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

21081384 is an abundant number, since it is smaller than the sum of its proper divisors (37967826).

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

21081384 is a wasteful number, since it uses less digits than its factorization.

21081384 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32551 (or 32538 counting only the distinct ones).

The product of its (nonzero) digits is 1536, while the sum is 27.

The square root of 21081384 is about 4591.4468307931. The cubic root of 21081384 is about 276.2483586780.

Adding to 21081384 its reverse (48318012), we get a palindrome (69399396).

The spelling of 21081384 in words is "twenty-one million, eighty-one thousand, three hundred eighty-four".