1997961638400 has 3840 divisors, whose sum is σ = 9912235576320. Its totient is φ = 382205952000.

The previous prime is 1997961638377. The next prime is 1997961638441. The reversal of 1997961638400 is 48361697991.

1997961638400 is a `hidden beast` number, since 1 + 9 + 9 + 7 + 9 + 616 + 3 + 8 + 4 + 0 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (3840).

It is a super-3 number, since 3×1997961638400³ (a number of 38 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is an unprimeable number.

It is a polite number, since it can be written in 383 ways as a sum of consecutive naturals, for example, 19781798350 + ... + 19781798450.

It is an arithmetic number, because the mean of its divisors is an integer number (2581311348).

Almost surely, 2^{1997961638400} is an apocalyptic number.

1997961638400 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 1997961638400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (4956117788160).

1997961638400 is an abundant number, since it is smaller than the sum of its proper divisors (7914273937920).

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

1997961638400 is a wasteful number, since it uses less digits than its factorization.

1997961638400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 212 (or 185 counting only the distinct ones).

The product of its (nonzero) digits is 17635968, while the sum is 63.

The spelling of 1997961638400 in words is "one trillion, nine hundred ninety-seven billion, nine hundred sixty-one million, six hundred thirty-eight thousand, four hundred".