161661612400 has 60 divisors (see below), whose sum is σ = 388803063672. Its totient is φ = 64596209920.

The previous prime is 161661612389. The next prime is 161661612407. The reversal of 161661612400 is 4216166161.

It is a super-2 number, since 2×161661612400² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (161661612407) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 165414 + ... + 592186.

Almost surely, 2^161661612400 is an apocalyptic number.

161661612400 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 161661612400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (194401531836).

161661612400 is an abundant number, since it is smaller than the sum of its proper divisors (227141451272).

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

161661612400 is a wasteful number, since it uses less digits than its factorization.

161661612400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 427738 (or 427727 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 34.

Adding to 161661612400 its reverse (4216166161), we get a palindrome (165877778561).

The spelling of 161661612400 in words is "one hundred sixty-one billion, six hundred sixty-one million, six hundred twelve thousand, four hundred".