161690121903 has 4 divisors (see below), whose sum is σ = 215586829208. Its totient is φ = 107793414600.

The previous prime is 161690121889. The next prime is 161690121907. The reversal of 161690121903 is 309121096161.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 309121096161 = 3 ⋅103040365387.

It is not a de Polignac number, because 161690121903 - 2⁵ = 161690121871 is a prime.

It is a super-2 number, since 2×161690121903² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161690121907) 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, 26948353648 + ... + 26948353653.

It is an arithmetic number, because the mean of its divisors is an integer number (53896707302).

Almost surely, 2^161690121903 is an apocalyptic number.

161690121903 is a deficient number, since it is larger than the sum of its proper divisors (53896707305).

161690121903 is an equidigital number, since it uses as much as digits as its factorization.

161690121903 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 53896707304.

The product of its (nonzero) digits is 17496, while the sum is 39.

The spelling of 161690121903 in words is "one hundred sixty-one billion, six hundred ninety million, one hundred twenty-one thousand, nine hundred three".