164723517821 has 4 divisors (see below), whose sum is σ = 164734307100. Its totient is φ = 164712728544.

The previous prime is 164723517799. The next prime is 164723517823. The reversal of 164723517821 is 128715327461.

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 111346346596 + 53377171225 = 333686^2 + 231035^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-164723517821 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 (164723517823) 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, 5371706 + ... + 5402283.

It is an arithmetic number, because the mean of its divisors is an integer number (41183576775).

Almost surely, 2^164723517821 is an apocalyptic number.

It is an amenable number.

164723517821 is a deficient number, since it is larger than the sum of its proper divisors (10789279).

164723517821 is a wasteful number, since it uses less digits than its factorization.

164723517821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10789278.

The product of its digits is 564480, while the sum is 47.

The spelling of 164723517821 in words is "one hundred sixty-four billion, seven hundred twenty-three million, five hundred seventeen thousand, eight hundred twenty-one".