121551661 has 16 divisors (see below), whose sum is σ = 153256320. Its totient is φ = 93646080.

The previous prime is 121551653. The next prime is 121551701. The reversal of 121551661 is 166155121.

It is a happy number.

It is not a de Polignac number, because 121551661 - 2³ = 121551653 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121551641) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2016 + ... + 15721.

It is an arithmetic number, because the mean of its divisors is an integer number (9578520).

Almost surely, 2^121551661 is an apocalyptic number.

121551661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

121551661 is a deficient number, since it is larger than the sum of its proper divisors (31704659).

121551661 is a wasteful number, since it uses less digits than its factorization.

121551661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17844.

The product of its digits is 1800, while the sum is 28.

The square root of 121551661 is about 11025.0469840269. The cubic root of 121551661 is about 495.3592752736.

The spelling of 121551661 in words is "one hundred twenty-one million, five hundred fifty-one thousand, six hundred sixty-one".