155561450021 has 4 divisors (see below), whose sum is σ = 160579561344. Its totient is φ = 150543338700.

The previous prime is 155561450017. The next prime is 155561450071. The reversal of 155561450021 is 120054165551.

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 155561450021 - 2² = 155561450017 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 (155561450071) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2509055615 + ... + 2509055676.

It is an arithmetic number, because the mean of its divisors is an integer number (40144890336).

Almost surely, 2^155561450021 is an apocalyptic number.

It is an amenable number.

155561450021 is a deficient number, since it is larger than the sum of its proper divisors (5018111323).

155561450021 is an equidigital number, since it uses as much as digits as its factorization.

155561450021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5018111322.

The product of its (nonzero) digits is 30000, while the sum is 35.

The spelling of 155561450021 in words is "one hundred fifty-five billion, five hundred sixty-one million, four hundred fifty thousand, twenty-one".