21780374 has 32 divisors (see below), whose sum is σ = 40974336. Its totient is φ = 8435520.

The previous prime is 21780361. The next prime is 21780377. The reversal of 21780374 is 47308712.

It is a happy number.

It is a Smith number, since the sum of its digits (32) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 21780374.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21780377) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 35579 + ... + 36185.

It is an arithmetic number, because the mean of its divisors is an integer number (1280448).

Almost surely, 2^21780374 is an apocalyptic number.

21780374 is a deficient number, since it is larger than the sum of its proper divisors (19193962).

21780374 is a wasteful number, since it uses less digits than its factorization.

21780374 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 860.

The product of its (nonzero) digits is 9408, while the sum is 32.

The square root of 21780374 is about 4666.9448250435. The cubic root of 21780374 is about 279.2683876532.

The spelling of 21780374 in words is "twenty-one million, seven hundred eighty thousand, three hundred seventy-four".