21780489 has 16 divisors (see below), whose sum is σ = 30008000. Its totient is φ = 14043456.

The previous prime is 21780487. The next prime is 21780491. The reversal of 21780489 is 98408712.

It is an interprime number because it is at equal distance from previous prime (21780487) and next prime (21780491).

It is not a de Polignac number, because 21780489 - 2¹ = 21780487 is a prime.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21780481) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13287 + ... + 14835.

It is an arithmetic number, because the mean of its divisors is an integer number (1875500).

Almost surely, 2^21780489 is an apocalyptic number.

It is an amenable number.

21780489 is a deficient number, since it is larger than the sum of its proper divisors (8227511).

21780489 is a wasteful number, since it uses less digits than its factorization.

21780489 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1704.

The product of its (nonzero) digits is 32256, while the sum is 39.

The square root of 21780489 is about 4666.9571457214. The cubic root of 21780489 is about 279.2688791631.

The spelling of 21780489 in words is "twenty-one million, seven hundred eighty thousand, four hundred eighty-nine".