21780490 has 8 divisors (see below), whose sum is σ = 39204900. Its totient is φ = 8712192.

The previous prime is 21780487. The next prime is 21780491. The reversal of 21780490 is 9408712.

It can be written as a sum of positive squares in 2 ways, for example, as 17614809 + 4165681 = 4197^2 + 2041^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not an unprimeable number, because it can be changed into a prime (21780491) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1089015 + ... + 1089034.

Almost surely, 2^21780490 is an apocalyptic number.

21780490 is a deficient number, since it is larger than the sum of its proper divisors (17424410).

21780490 is a wasteful number, since it uses less digits than its factorization.

21780490 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2178056.

The product of its (nonzero) digits is 4032, while the sum is 31.

The square root of 21780490 is about 4666.9572528576. The cubic root of 21780490 is about 279.2688834371.

The spelling of 21780490 in words is "twenty-one million, seven hundred eighty thousand, four hundred ninety".