161661612401 has 4 divisors (see below), whose sum is σ = 161828791872. Its totient is φ = 161494432932.

The previous prime is 161661612389. The next prime is 161661612407. The reversal of 161661612401 is 104216166161.

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, and also an emirpimes, since its reverse is a distinct semiprime: 104216166161 = 11593 ⋅8989577.

It is a cyclic number.

It is not a de Polignac number, because 161661612401 - 2³⁰ = 160587870577 is a prime.

It is a super-2 number, since 2×161661612401² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (161661612407) 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, 83588285 + ... + 83590218.

It is an arithmetic number, because the mean of its divisors is an integer number (40457197968).

Almost surely, 2^161661612401 is an apocalyptic number.

It is an amenable number.

161661612401 is a deficient number, since it is larger than the sum of its proper divisors (167179471).

161661612401 is an equidigital number, since it uses as much as digits as its factorization.

161661612401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 167179470.

The product of its (nonzero) digits is 10368, while the sum is 35.

Adding to 161661612401 its reverse (104216166161), we get a palindrome (265877778562).

The spelling of 161661612401 in words is "one hundred sixty-one billion, six hundred sixty-one million, six hundred twelve thousand, four hundred one".