61491047209 has 2 divisors, whose sum is σ = 61491047210. Its totient is φ = 61491047208.

The previous prime is 61491047207. The next prime is 61491047221. The reversal of 61491047209 is 90274019416.

61491047209 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 56140563600 + 5350483609 = 236940^2 + 73147^2 .

It is a cyclic number.

It is not a de Polignac number, because 61491047209 - 2¹ = 61491047207 is a prime.

It is a super-2 number, since 2×61491047209² (a number of 22 digits) contains 22 as substring.

Together with 61491047207, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (61491047203) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30745523604 + 30745523605.

It is an arithmetic number, because the mean of its divisors is an integer number (30745523605).

Almost surely, 2^61491047209 is an apocalyptic number.

It is an amenable number.

61491047209 is a deficient number, since it is larger than the sum of its proper divisors (1).

61491047209 is an equidigital number, since it uses as much as digits as its factorization.

61491047209 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 108864, while the sum is 43.

The spelling of 61491047209 in words is "sixty-one billion, four hundred ninety-one million, forty-seven thousand, two hundred nine".