161720420400 has 1800 divisors, whose sum is σ = 748276607232. Its totient is φ = 32731776000.

The previous prime is 161720420369. The next prime is 161720420431. The reversal of 161720420400 is 4024027161.

161720420400 is a `hidden beast` number, since 1 + 617 + 2 + 0 + 4 + 2 + 0 + 40 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (161720420369) and next prime (161720420431).

It is a tau number, because it is divible by the number of its divisors (1800).

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 359 ways as a sum of consecutive naturals, for example, 1948438759 + ... + 1948438841.

Almost surely, 2^161720420400 is an apocalyptic number.

161720420400 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 161720420400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (374138303616).

161720420400 is an abundant number, since it is smaller than the sum of its proper divisors (586556186832).

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

161720420400 is a wasteful number, since it uses less digits than its factorization.

161720420400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 213 (or 182 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

Adding to 161720420400 its reverse (4024027161), we get a palindrome (165744447561).

The spelling of 161720420400 in words is "one hundred sixty-one billion, seven hundred twenty million, four hundred twenty thousand, four hundred".