61566206221 has 4 divisors (see below), whose sum is σ = 66302068252. Its totient is φ = 56830344192.

The previous prime is 61566206167. The next prime is 61566206227. The reversal of 61566206221 is 12260266516.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 25924542121 + 35641664100 = 161011^2 + 188790^2 .

It is a cyclic number.

It is not a de Polignac number, because 61566206221 - 2²¹ = 61564109069 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 (61566206227) 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, 2367930996 + ... + 2367931021.

It is an arithmetic number, because the mean of its divisors is an integer number (16575517063).

Almost surely, 2^61566206221 is an apocalyptic number.

It is an amenable number.

61566206221 is a deficient number, since it is larger than the sum of its proper divisors (4735862031).

61566206221 is a wasteful number, since it uses less digits than its factorization.

61566206221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4735862030.

The product of its (nonzero) digits is 51840, while the sum is 37.

The spelling of 61566206221 in words is "sixty-one billion, five hundred sixty-six million, two hundred six thousand, two hundred twenty-one".