155136721 has 4 divisors (see below), whose sum is σ = 155605744. Its totient is φ = 154667700.

The previous prime is 155136719. The next prime is 155136749. The reversal of 155136721 is 127631551.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 155136721 - 2¹ = 155136719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (155136521) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 234015 + ... + 234676.

It is an arithmetic number, because the mean of its divisors is an integer number (38901436).

Almost surely, 2^155136721 is an apocalyptic number.

It is an amenable number.

155136721 is a deficient number, since it is larger than the sum of its proper divisors (469023).

155136721 is an equidigital number, since it uses as much as digits as its factorization.

155136721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 469022.

The product of its digits is 6300, while the sum is 31.

The square root of 155136721 is about 12455.3892351865. The cubic root of 155136721 is about 537.3264293357.

The spelling of 155136721 in words is "one hundred fifty-five million, one hundred thirty-six thousand, seven hundred twenty-one".