121661531640 has 96 divisors (see below), whose sum is σ = 431345444400. Its totient is φ = 29493703680.

The previous prime is 121661531617. The next prime is 121661531659. The reversal of 121661531640 is 46135166121.

121661531640 is a `hidden beast` number, since 1 + 2 + 1 + 6 + 6 + 1 + 5 + 3 + 1 + 640 = 666.

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

It is a junction number, because it is equal to n+sod(n) for n = 121661531595 and 121661531604.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 15357345 + ... + 15365264.

Almost surely, 2^121661531640 is an apocalyptic number.

121661531640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

121661531640 is an abundant number, since it is smaller than the sum of its proper divisors (309683912760).

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

121661531640 is a wasteful number, since it uses less digits than its factorization.

121661531640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30722637 (or 30722630 counting only the distinct ones).

The product of its (nonzero) digits is 25920, while the sum is 36.

Adding to 121661531640 its reverse (46135166121), we get a palindrome (167796697761).

The spelling of 121661531640 in words is "one hundred twenty-one billion, six hundred sixty-one million, five hundred thirty-one thousand, six hundred forty".