20156909 has 6 divisors (see below), whose sum is σ = 20298510. Its totient is φ = 20016216.

The previous prime is 20156893. The next prime is 20156921. The reversal of 20156909 is 90965102.

It can be written as a sum of positive squares in only one way, i.e., 19166884 + 990025 = 4378^2 + 995^2 .

It is not a de Polignac number, because 20156909 - 2⁴ = 20156893 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20156959) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 39347 + ... + 39855.

It is an arithmetic number, because the mean of its divisors is an integer number (3383085).

Almost surely, 2^20156909 is an apocalyptic number.

It is an amenable number.

20156909 is a deficient number, since it is larger than the sum of its proper divisors (141601).

20156909 is an frugal number, since it uses more digits than its factorization.

20156909 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 907 (or 708 counting only the distinct ones).

The product of its (nonzero) digits is 4860, while the sum is 32.

The square root of 20156909 is about 4489.6446407260. The cubic root of 20156909 is about 272.1497742389.

The spelling of 20156909 in words is "twenty million, one hundred fifty-six thousand, nine hundred nine".