661550121 has 48 divisors (see below), whose sum is σ = 1047939984. Its totient is φ = 400453632.

The previous prime is 661550119. The next prime is 661550147. The reversal of 661550121 is 121055166.

It is a happy number.

It can be written as a sum of positive squares in 8 ways, for example, as 14356521 + 647193600 = 3789^2 + 25440^2 .

It is not a de Polignac number, because 661550121 - 2¹ = 661550119 is a prime.

It is a super-2 number, since 2×661550121² = 875297125190229282, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (661550191) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 775131 + ... + 775983.

It is an arithmetic number, because the mean of its divisors is an integer number (21832083).

Almost surely, 2^661550121 is an apocalyptic number.

It is an amenable number.

661550121 is a deficient number, since it is larger than the sum of its proper divisors (386389863).

661550121 is a wasteful number, since it uses less digits than its factorization.

661550121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1050 (or 1047 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 27.

The square root of 661550121 is about 25720.6166527943. The cubic root of 661550121 is about 871.3398656881.

The spelling of 661550121 in words is "six hundred sixty-one million, five hundred fifty thousand, one hundred twenty-one".