161211720 has 32 divisors (see below), whose sum is σ = 483635520. Its totient is φ = 42989760.

The previous prime is 161211707. The next prime is 161211733. The reversal of 161211720 is 27112161.

It is a happy number.

161211720 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (161211707) and next prime (161211733).

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, 671596 + ... + 671835.

It is an arithmetic number, because the mean of its divisors is an integer number (15113610).

Almost surely, 2^161211720 is an apocalyptic number.

161211720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

161211720 is an abundant number, since it is smaller than the sum of its proper divisors (322423800).

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

161211720 is a wasteful number, since it uses less digits than its factorization.

161211720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1343445 (or 1343441 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 21.

The square root of 161211720 is about 12696.9177362067. The cubic root of 161211720 is about 544.2505423934.

Adding to 161211720 its reverse (27112161), we get a palindrome (188323881).

The spelling of 161211720 in words is "one hundred sixty-one million, two hundred eleven thousand, seven hundred twenty".