155821813 has 16 divisors (see below), whose sum is σ = 192412800. Its totient is φ = 125700288.

The previous prime is 155821807. The next prime is 155821859. The reversal of 155821813 is 318128551.

It is not a de Polignac number, because 155821813 - 2¹⁷ = 155690741 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (155821013) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7531 + ... + 19192.

It is an arithmetic number, because the mean of its divisors is an integer number (12025800).

Almost surely, 2^155821813 is an apocalyptic number.

It is an amenable number.

155821813 is a deficient number, since it is larger than the sum of its proper divisors (36590987).

155821813 is an equidigital number, since it uses as much as digits as its factorization.

155821813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 26761 (or 26747 counting only the distinct ones).

The product of its digits is 9600, while the sum is 34.

The square root of 155821813 is about 12482.8607698716. The cubic root of 155821813 is about 538.1162219028.

The spelling of 155821813 in words is "one hundred fifty-five million, eight hundred twenty-one thousand, eight hundred thirteen".