161645551409 has 2 divisors, whose sum is σ = 161645551410. Its totient is φ = 161645551408.

The previous prime is 161645551393. The next prime is 161645551427. The reversal of 161645551409 is 904155546161.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 128203383025 + 33442168384 = 358055^2 + 182872^2 .

It is a cyclic number.

It is not a de Polignac number, because 161645551409 - 2⁴ = 161645551393 is a prime.

It is a super-2 number, since 2×161645551409² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (161645551709) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 80822775704 + 80822775705.

It is an arithmetic number, because the mean of its divisors is an integer number (80822775705).

Almost surely, 2^161645551409 is an apocalyptic number.

It is an amenable number.

161645551409 is a deficient number, since it is larger than the sum of its proper divisors (1).

161645551409 is an equidigital number, since it uses as much as digits as its factorization.

161645551409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 648000, while the sum is 47.

The spelling of 161645551409 in words is "one hundred sixty-one billion, six hundred forty-five million, five hundred fifty-one thousand, four hundred nine".