664581417261 has 4 divisors (see below), whose sum is σ = 886108556352. Its totient is φ = 443054278172.

The previous prime is 664581417259. The next prime is 664581417287. The reversal of 664581417261 is 162714185466.

664581417261 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 a cyclic number.

It is not a de Polignac number, because 664581417261 - 2¹ = 664581417259 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664581415261) 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, 110763569541 + ... + 110763569546.

It is an arithmetic number, because the mean of its divisors is an integer number (221527139088).

Almost surely, 2^664581417261 is an apocalyptic number.

It is an amenable number.

664581417261 is a deficient number, since it is larger than the sum of its proper divisors (221527139091).

664581417261 is a wasteful number, since it uses less digits than its factorization.

664581417261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 221527139090.

The product of its digits is 1935360, while the sum is 51.

It can be divided in two parts, 6645814 and 17261, that added together give a triangular number (6663075 = T₃₆₅₀).

The spelling of 664581417261 in words is "six hundred sixty-four billion, five hundred eighty-one million, four hundred seventeen thousand, two hundred sixty-one".