161121690 has 64 divisors (see below), whose sum is σ = 431481600. Its totient is φ = 42783552.

The previous prime is 161121683. The next prime is 161121703. The reversal of 161121690 is 96121161.

It is a super-2 number, since 2×161121690² = 51920397976912200, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 69876 + ... + 72144.

It is an arithmetic number, because the mean of its divisors is an integer number (6741900).

Almost surely, 2^161121690 is an apocalyptic number.

161121690 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 161121690, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (215740800).

161121690 is an abundant number, since it is smaller than the sum of its proper divisors (270359910).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

161121690 is a wasteful number, since it uses less digits than its factorization.

161121690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2548 (or 2542 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 27.

The square root of 161121690 is about 12693.3718924484. The cubic root of 161121690 is about 544.1492098095.

The spelling of 161121690 in words is "one hundred sixty-one million, one hundred twenty-one thousand, six hundred ninety".