21906685 has 8 divisors (see below), whose sum is σ = 26368056. Its totient is φ = 17472000.

The previous prime is 21906673. The next prime is 21906697. The reversal of 21906685 is 58660912.

It is an interprime number because it is at equal distance from previous prime (21906673) and next prime (21906697).

It can be written as a sum of positive squares in 4 ways, for example, as 395641 + 21511044 = 629^2 + 4638^2 .

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

It is not a de Polignac number, because 21906685 - 2⁹ = 21906173 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4816 + ... + 8185.

It is an arithmetic number, because the mean of its divisors is an integer number (3296007).

Almost surely, 2^21906685 is an apocalyptic number.

It is an amenable number.

21906685 is a deficient number, since it is larger than the sum of its proper divisors (4461371).

21906685 is a wasteful number, since it uses less digits than its factorization.

21906685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13343.

The product of its (nonzero) digits is 25920, while the sum is 37.

The square root of 21906685 is about 4680.4577767565. The cubic root of 21906685 is about 279.8072014596.

The spelling of 21906685 in words is "twenty-one million, nine hundred six thousand, six hundred eighty-five".