121778661 has 4 divisors (see below), whose sum is σ = 162371552. Its totient is φ = 81185772.

The previous prime is 121778659. The next prime is 121778669. The reversal of 121778661 is 166877121.

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 121778661 - 2¹ = 121778659 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121778669) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20296441 + ... + 20296446.

It is an arithmetic number, because the mean of its divisors is an integer number (40592888).

Almost surely, 2^121778661 is an apocalyptic number.

It is an amenable number.

121778661 is a deficient number, since it is larger than the sum of its proper divisors (40592891).

121778661 is an equidigital number, since it uses as much as digits as its factorization.

121778661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40592890.

The product of its digits is 28224, while the sum is 39.

The square root of 121778661 is about 11035.3369228130. The cubic root of 121778661 is about 495.6674477505.

The spelling of 121778661 in words is "one hundred twenty-one million, seven hundred seventy-eight thousand, six hundred sixty-one".