21906985 has 8 divisors (see below), whose sum is σ = 26481096. Its totient is φ = 17397120.

The previous prime is 21906961. The next prime is 21907007. The reversal of 21906985 is 58960912.

It can be written as a sum of positive squares in 4 ways, for example, as 200704 + 21706281 = 448^2 + 4659^2 .

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

It is not a de Polignac number, because 21906985 - 2⁵ = 21906953 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15306 + ... + 16675.

It is an arithmetic number, because the mean of its divisors is an integer number (3310137).

Almost surely, 2^21906985 is an apocalyptic number.

It is an amenable number.

21906985 is a deficient number, since it is larger than the sum of its proper divisors (4574111).

21906985 is a wasteful number, since it uses less digits than its factorization.

21906985 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32123.

The product of its (nonzero) digits is 38880, while the sum is 40.

The square root of 21906985 is about 4680.4898247940. The cubic root of 21906985 is about 279.8084787223.

The spelling of 21906985 in words is "twenty-one million, nine hundred six thousand, nine hundred eighty-five".