20906905 has 8 divisors (see below), whose sum is σ = 25249032. Its totient is φ = 16618368.

The previous prime is 20906903. The next prime is 20906917. The reversal of 20906905 is 50960902.

It can be written as a sum of positive squares in 4 ways, for example, as 5875776 + 15031129 = 2424^2 + 3877^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 20906905 - 2¹ = 20906903 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20906903) by changing a digit.

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 7 ways as a sum of consecutive naturals, for example, 12532 + ... + 14101.

It is an arithmetic number, because the mean of its divisors is an integer number (3156129).

Almost surely, 2^20906905 is an apocalyptic number.

It is an amenable number.

20906905 is a deficient number, since it is larger than the sum of its proper divisors (4342127).

20906905 is a wasteful number, since it uses less digits than its factorization.

20906905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26795.

The product of its (nonzero) digits is 4860, while the sum is 31.

The square root of 20906905 is about 4572.4069154002. The cubic root of 20906905 is about 275.4841279258.

The spelling of 20906905 in words is "twenty million, nine hundred six thousand, nine hundred five".