161391220 has 12 divisors (see below), whose sum is σ = 338921604. Its totient is φ = 64556480.

The previous prime is 161391199. The next prime is 161391227. The reversal of 161391220 is 22193161.

161391220 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 77228944 + 84162276 = 8788^2 + 9174^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161391227) 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, 4034761 + ... + 4034800.

It is an arithmetic number, because the mean of its divisors is an integer number (28243467).

Almost surely, 2^161391220 is an apocalyptic number.

161391220 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

161391220 is an abundant number, since it is smaller than the sum of its proper divisors (177530384).

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

161391220 is a wasteful number, since it uses less digits than its factorization.

161391220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8069570 (or 8069568 counting only the distinct ones).

The product of its (nonzero) digits is 648, while the sum is 25.

The square root of 161391220 is about 12703.9844143481. The cubic root of 161391220 is about 544.4524647190.

The spelling of 161391220 in words is "one hundred sixty-one million, three hundred ninety-one thousand, two hundred twenty".