661775326819 has 4 divisors (see below), whose sum is σ = 668200330096. Its totient is φ = 655350323544.

The previous prime is 661775326811. The next prime is 661775326843. The reversal of 661775326819 is 918623577166.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 661775326819 - 2³ = 661775326811 is a prime.

It is a super-2 number, since 2×661775326819² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661775326811) 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, 3212501484 + ... + 3212501689.

It is an arithmetic number, because the mean of its divisors is an integer number (167050082524).

Almost surely, 2^661775326819 is an apocalyptic number.

661775326819 is a deficient number, since it is larger than the sum of its proper divisors (6425003277).

661775326819 is a wasteful number, since it uses less digits than its factorization.

661775326819 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6425003276.

The product of its digits is 22861440, while the sum is 61.

The spelling of 661775326819 in words is "six hundred sixty-one billion, seven hundred seventy-five million, three hundred twenty-six thousand, eight hundred nineteen".