161991744 has 56 divisors (see below), whose sum is σ = 436717440. Its totient is φ = 52975104.

The previous prime is 161991727. The next prime is 161991761. The reversal of 161991744 is 447199161.

It is an interprime number because it is at equal distance from previous prime (161991727) and next prime (161991761).

It is a junction number, because it is equal to n+sod(n) for n = 161991696 and 161991705.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2217 + ... + 18135.

Almost surely, 2^161991744 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 161991744, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (218358720).

161991744 is an abundant number, since it is smaller than the sum of its proper divisors (274725696).

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

161991744 is a wasteful number, since it uses less digits than its factorization.

161991744 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15987 (or 15977 counting only the distinct ones).

The product of its digits is 54432, while the sum is 42.

The square root of 161991744 is about 12727.5977309153. The cubic root of 161991744 is about 545.1269171074.

It can be divided in two parts, 161991 and 744, that added together give a triangular number (162735 = T₅₇₀).

The spelling of 161991744 in words is "one hundred sixty-one million, nine hundred ninety-one thousand, seven hundred forty-four".