20840155 has 16 divisors (see below), whose sum is σ = 28658880. Its totient is φ = 14251392.

The previous prime is 20840123. The next prime is 20840167. The reversal of 20840155 is 55104802.

It is a cyclic number.

It is not a de Polignac number, because 20840155 - 2⁵ = 20840123 is a prime.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18961 + ... + 20029.

It is an arithmetic number, because the mean of its divisors is an integer number (1791180).

Almost surely, 2^20840155 is an apocalyptic number.

20840155 is a deficient number, since it is larger than the sum of its proper divisors (7818725).

20840155 is a wasteful number, since it uses less digits than its factorization.

20840155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1638.

The product of its (nonzero) digits is 1600, while the sum is 25.

The square root of 20840155 is about 4565.1018608570. The cubic root of 20840155 is about 275.1906336599.

Adding to 20840155 its reverse (55104802), we get a palindrome (75944957).

The spelling of 20840155 in words is "twenty million, eight hundred forty thousand, one hundred fifty-five".