21908985 has 16 divisors (see below), whose sum is σ = 40062336. Its totient is φ = 10015488.

The previous prime is 21908959. The next prime is 21908987. The reversal of 21908985 is 58980912.

It is a happy number.

It is not a de Polignac number, because 21908985 - 2¹⁰ = 21907961 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21908987) 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, 104224 + ... + 104433.

It is an arithmetic number, because the mean of its divisors is an integer number (2503896).

Almost surely, 2^21908985 is an apocalyptic number.

It is an amenable number.

21908985 is a deficient number, since it is larger than the sum of its proper divisors (18153351).

21908985 is a wasteful number, since it uses less digits than its factorization.

21908985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 208672.

The product of its (nonzero) digits is 51840, while the sum is 42.

The square root of 21908985 is about 4680.7034727699. The cubic root of 21908985 is about 279.8169935092.

It can be divided in two parts, 2190 and 8985, that added together give a triangular number (11175 = T₁₄₉).

The spelling of 21908985 in words is "twenty-one million, nine hundred eight thousand, nine hundred eighty-five".