121681981 has 4 divisors (see below), whose sum is σ = 122131264. Its totient is φ = 121232700.

The previous prime is 121681951. The next prime is 121681993. The reversal of 121681981 is 189186121.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-121681981 is a prime.

It is a super-2 number, since 2×121681981² = 29613009000168722, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 121681981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (121681921) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 224235 + ... + 224776.

It is an arithmetic number, because the mean of its divisors is an integer number (30532816).

Almost surely, 2^121681981 is an apocalyptic number.

It is an amenable number.

121681981 is a deficient number, since it is larger than the sum of its proper divisors (449283).

121681981 is an equidigital number, since it uses as much as digits as its factorization.

121681981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 449282.

The product of its digits is 6912, while the sum is 37.

The square root of 121681981 is about 11030.9555796404. The cubic root of 121681981 is about 495.5362430015.

The spelling of 121681981 in words is "one hundred twenty-one million, six hundred eighty-one thousand, nine hundred eighty-one".