19805901979 has 4 divisors (see below), whose sum is σ = 20667028176. Its totient is φ = 18944775784.

The previous prime is 19805901961. The next prime is 19805902049. The reversal of 19805901979 is 97910950891.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 19805901979 - 2⁷ = 19805901851 is a prime.

It is a super-2 number, since 2×19805901979² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19805901679) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 430563064 + ... + 430563109.

It is an arithmetic number, because the mean of its divisors is an integer number (5166757044).

Almost surely, 2^19805901979 is an apocalyptic number.

19805901979 is a deficient number, since it is larger than the sum of its proper divisors (861126197).

19805901979 is an equidigital number, since it uses as much as digits as its factorization.

19805901979 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 861126196.

The product of its (nonzero) digits is 1837080, while the sum is 58.

The spelling of 19805901979 in words is "nineteen billion, eight hundred five million, nine hundred one thousand, nine hundred seventy-nine".