21489890 has 8 divisors (see below), whose sum is σ = 38681820. Its totient is φ = 8595952.

The previous prime is 21489883. The next prime is 21489901. The reversal of 21489890 is 9898412.

It can be written as a sum of positive squares in 2 ways, for example, as 21242881 + 247009 = 4609^2 + 497^2 .

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

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, 1074485 + ... + 1074504.

Almost surely, 2^21489890 is an apocalyptic number.

21489890 is a deficient number, since it is larger than the sum of its proper divisors (17191930).

21489890 is a wasteful number, since it uses less digits than its factorization.

21489890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2148996.

The product of its (nonzero) digits is 41472, while the sum is 41.

The square root of 21489890 is about 4635.7189302200. The cubic root of 21489890 is about 278.0212964380.

The spelling of 21489890 in words is "twenty-one million, four hundred eighty-nine thousand, eight hundred ninety".