161221236 has 24 divisors (see below), whose sum is σ = 410381664. Its totient is φ = 48854880.

The previous prime is 161221219. The next prime is 161221241. The reversal of 161221236 is 632122161.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

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, 610555 + ... + 610818.

It is an arithmetic number, because the mean of its divisors is an integer number (17099236).

Almost surely, 2^161221236 is an apocalyptic number.

It is an amenable number.

161221236 is an abundant number, since it is smaller than the sum of its proper divisors (249160428).

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

161221236 is a wasteful number, since it uses less digits than its factorization.

161221236 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1221391 (or 1221389 counting only the distinct ones).

The product of its digits is 864, while the sum is 24.

The square root of 161221236 is about 12697.2924672940. The cubic root of 161221236 is about 544.2612508503.

Adding to 161221236 its reverse (632122161), we get a palindrome (793343397).

The spelling of 161221236 in words is "one hundred sixty-one million, two hundred twenty-one thousand, two hundred thirty-six".