161621720218 has 64 divisors (see below), whose sum is σ = 288568590336. Its totient is φ = 66432960000.

The previous prime is 161621720201. The next prime is 161621720263. The reversal of 161621720218 is 812027126161.

It is a super-2 number, since 2×161621720218² (a number of 23 digits) contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 30601738 + ... + 30607018.

It is an arithmetic number, because the mean of its divisors is an integer number (4508884224).

Almost surely, 2^161621720218 is an apocalyptic number.

161621720218 is a deficient number, since it is larger than the sum of its proper divisors (126946870118).

161621720218 is a wasteful number, since it uses less digits than its factorization.

161621720218 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5939.

The product of its (nonzero) digits is 16128, while the sum is 37.

Adding to 161621720218 its reverse (812027126161), we get a palindrome (973648846379).

The spelling of 161621720218 in words is "one hundred sixty-one billion, six hundred twenty-one million, seven hundred twenty thousand, two hundred eighteen".