21780368 has 10 divisors (see below), whose sum is σ = 42199494. Its totient is φ = 10890176.

The previous prime is 21780361. The next prime is 21780377. The reversal of 21780368 is 86308712.

It can be written as a sum of positive squares in only one way, i.e., 18215824 + 3564544 = 4268^2 + 1888^2 .

It is not an unprimeable number, because it can be changed into a prime (21780361) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 680621 + ... + 680652.

Almost surely, 2^21780368 is an apocalyptic number.

It is an amenable number.

21780368 is a deficient number, since it is larger than the sum of its proper divisors (20419126).

21780368 is a wasteful number, since it uses less digits than its factorization.

21780368 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1361281 (or 1361275 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 35.

The square root of 21780368 is about 4666.9441822246. The cubic root of 21780368 is about 279.2683620092.

The spelling of 21780368 in words is "twenty-one million, seven hundred eighty thousand, three hundred sixty-eight".