20905890 has 32 divisors (see below), whose sum is σ = 52816320. Its totient is φ = 5281344.

The previous prime is 20905877. The next prime is 20905901. The reversal of 20905890 is 9850902.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 17769 + ... + 18908.

It is an arithmetic number, because the mean of its divisors is an integer number (1650510).

Almost surely, 2^20905890 is an apocalyptic number.

20905890 is an abundant number, since it is smaller than the sum of its proper divisors (31910430).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20905890 is a wasteful number, since it uses less digits than its factorization.

20905890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36706.

The product of its (nonzero) digits is 6480, while the sum is 33.

The square root of 20905890 is about 4572.2959221818. The cubic root of 20905890 is about 275.4796697349.

The spelling of 20905890 in words is "twenty million, nine hundred five thousand, eight hundred ninety".