155616561655621 has 4 divisors (see below), whose sum is σ = 169763521806144. Its totient is φ = 141469601505100.

The previous prime is 155616561655537. The next prime is 155616561655627. The reversal of 155616561655621 is 126556165616551.

It is a happy number.

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 not a de Polignac number, because 155616561655621 - 2²¹ = 155616559558469 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 155616561655621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (155616561655627) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7073480075245 + ... + 7073480075266.

It is an arithmetic number, because the mean of its divisors is an integer number (42440880451536).

Almost surely, 2^{155616561655621} is an apocalyptic number.

155616561655621 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

155616561655621 is a deficient number, since it is larger than the sum of its proper divisors (14146960150523).

155616561655621 is a wasteful number, since it uses less digits than its factorization.

155616561655621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14146960150522.

The product of its digits is 48600000, while the sum is 61.

The spelling of 155616561655621 in words is "one hundred fifty-five trillion, six hundred sixteen billion, five hundred sixty-one million, six hundred fifty-five thousand, six hundred twenty-one".