21685490 has 8 divisors (see below), whose sum is σ = 39033900. Its totient is φ = 8674192.

The previous prime is 21685487. The next prime is 21685507. The reversal of 21685490 is 9458612.

It can be written as a sum of positive squares in 2 ways, for example, as 21224449 + 461041 = 4607^2 + 679^2 .

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

It is a self number, because there is not a number n which added to its sum of digits gives 21685490.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 1084265 + ... + 1084284.

Almost surely, 2^21685490 is an apocalyptic number.

21685490 is a deficient number, since it is larger than the sum of its proper divisors (17348410).

21685490 is a wasteful number, since it uses less digits than its factorization.

21685490 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2168556.

The product of its (nonzero) digits is 17280, while the sum is 35.

The square root of 21685490 is about 4656.7681926418. The cubic root of 21685490 is about 278.8622624896.

The spelling of 21685490 in words is "twenty-one million, six hundred eighty-five thousand, four hundred ninety".