121557661020 has 36 divisors (see below), whose sum is σ = 368724905640. Its totient is φ = 32415376224.

The previous prime is 121557661013. The next prime is 121557661051. The reversal of 121557661020 is 20166755121.

121557661020 is a `hidden beast` number, since 1 + 2 + 1 + 5 + 576 + 61 + 0 + 20 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 337659990 + ... + 337660349.

It is an arithmetic number, because the mean of its divisors is an integer number (10242358490).

Almost surely, 2^121557661020 is an apocalyptic number.

121557661020 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

121557661020 is an abundant number, since it is smaller than the sum of its proper divisors (247167244620).

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

121557661020 is a wasteful number, since it uses less digits than its factorization.

121557661020 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 675320354 (or 675320349 counting only the distinct ones).

The product of its (nonzero) digits is 25200, while the sum is 36.

The spelling of 121557661020 in words is "one hundred twenty-one billion, five hundred fifty-seven million, six hundred sixty-one thousand, twenty".