155661610121 has 4 divisors (see below), whose sum is σ = 157116391632. Its totient is φ = 154206828612.

The previous prime is 155661610109. The next prime is 155661610127. The reversal of 155661610121 is 121016166551.

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 a cyclic number.

It is not a de Polignac number, because 155661610121 - 2⁶ = 155661610057 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (155661610127) 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, 727390595 + ... + 727390808.

It is an arithmetic number, because the mean of its divisors is an integer number (39279097908).

Almost surely, 2^155661610121 is an apocalyptic number.

It is an amenable number.

155661610121 is a deficient number, since it is larger than the sum of its proper divisors (1454781511).

155661610121 is a wasteful number, since it uses less digits than its factorization.

155661610121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1454781510.

The product of its (nonzero) digits is 10800, while the sum is 35.

Adding to 155661610121 its reverse (121016166551), we get a palindrome (276677776672).

The spelling of 155661610121 in words is "one hundred fifty-five billion, six hundred sixty-one million, six hundred ten thousand, one hundred twenty-one".