661364121600 has 1008 divisors, whose sum is σ = 2916442419072. Its totient is φ = 139505172480.

The previous prime is 661364121599. The next prime is 661364121617. The reversal of 661364121600 is 6121463166.

It is a happy number.

661364121600 is a `hidden beast` number, since 6 + 6 + 1 + 3 + 6 + 41 + 2 + 1 + 600 = 666.

It is a tau number, because it is divible by the number of its divisors (1008).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 167729229 + ... + 167733171.

Almost surely, 2^661364121600 is an apocalyptic number.

661364121600 is a gapful number since it is divisible by the number (60) 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 661364121600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1458221209536).

661364121600 is an abundant number, since it is smaller than the sum of its proper divisors (2255078297472).

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

661364121600 is a wasteful number, since it uses less digits than its factorization.

661364121600 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4005 (or 3973 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 36.

Adding to 661364121600 its reverse (6121463166), we get a palindrome (667485584766).

The spelling of 661364121600 in words is "six hundred sixty-one billion, three hundred sixty-four million, one hundred twenty-one thousand, six hundred".