163951780621 has 2 divisors, whose sum is σ = 163951780622. Its totient is φ = 163951780620.

The previous prime is 163951780591. The next prime is 163951780661. The reversal of 163951780621 is 126087159361.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 102787566025 + 61164214596 = 320605^2 + 247314^2 .

It is a cyclic number.

It is not a de Polignac number, because 163951780621 - 2⁵ = 163951780589 is a prime.

It is a super-2 number, since 2×163951780621² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (163951780661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 81975890310 + 81975890311.

It is an arithmetic number, because the mean of its divisors is an integer number (81975890311).

Almost surely, 2^163951780621 is an apocalyptic number.

It is an amenable number.

163951780621 is a deficient number, since it is larger than the sum of its proper divisors (1).

163951780621 is an equidigital number, since it uses as much as digits as its factorization.

163951780621 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 544320, while the sum is 49.

The spelling of 163951780621 in words is "one hundred sixty-three billion, nine hundred fifty-one million, seven hundred eighty thousand, six hundred twenty-one".