121686561 has 12 divisors (see below), whose sum is σ = 186109092. Its totient is φ = 76352256.

The previous prime is 121686541. The next prime is 121686571. The reversal of 121686561 is 165686121.

121686561 is a `hidden beast` number, since 1 + 2 + 16 + 86 + 561 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 94187025 + 27499536 = 9705^2 + 5244^2 .

It is not a de Polignac number, because 121686561 - 2⁵ = 121686529 is a prime.

It is not an unprimeable number, because it can be changed into a prime (121686541) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 397516 + ... + 397821.

It is an arithmetic number, because the mean of its divisors is an integer number (15509091).

Almost surely, 2^121686561 is an apocalyptic number.

It is an amenable number.

121686561 is a deficient number, since it is larger than the sum of its proper divisors (64422531).

121686561 is a wasteful number, since it uses less digits than its factorization.

121686561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 795360 (or 795357 counting only the distinct ones).

The product of its digits is 17280, while the sum is 36.

The square root of 121686561 is about 11031.1631752957. The cubic root of 121686561 is about 495.5424601025.

The spelling of 121686561 in words is "one hundred twenty-one million, six hundred eighty-six thousand, five hundred sixty-one".