155243981 has 2 divisors, whose sum is σ = 155243982. Its totient is φ = 155243980.

The previous prime is 155243929. The next prime is 155243993. The reversal of 155243981 is 189342551.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 126450025 + 28793956 = 11245^2 + 5366^2 .

It is a cyclic number.

It is not a de Polignac number, because 155243981 - 2¹⁰ = 155242957 is a prime.

It is a super-2 number, since 2×155243981² = 48201387273456722, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is equal to p_8722496 and since 155243981 and 8722496 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (155246981) 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 as a sum of consecutive naturals, namely, 77621990 + 77621991.

It is an arithmetic number, because the mean of its divisors is an integer number (77621991).

Almost surely, 2^155243981 is an apocalyptic number.

It is an amenable number.

155243981 is a deficient number, since it is larger than the sum of its proper divisors (1).

155243981 is an equidigital number, since it uses as much as digits as its factorization.

155243981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 43200, while the sum is 38.

The square root of 155243981 is about 12459.6942578861. The cubic root of 155243981 is about 537.4502348734.

The spelling of 155243981 in words is "one hundred fifty-five million, two hundred forty-three thousand, nine hundred eighty-one".