19811721950 has 24 divisors (see below), whose sum is σ = 36855923808. Its totient is φ = 7923372480.

The previous prime is 19811721911. The next prime is 19811721959. The reversal of 19811721950 is 5912711891.

It is a super-2 number, since 2×19811721950² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19811721959) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 305594 + ... + 364706.

It is an arithmetic number, because the mean of its divisors is an integer number (1535663492).

Almost surely, 2^19811721950 is an apocalyptic number.

19811721950 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

19811721950 is a deficient number, since it is larger than the sum of its proper divisors (17044201858).

19811721950 is a wasteful number, since it uses less digits than its factorization.

19811721950 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 65828 (or 65823 counting only the distinct ones).

The product of its (nonzero) digits is 45360, while the sum is 44.

The spelling of 19811721950 in words is "nineteen billion, eight hundred eleven million, seven hundred twenty-one thousand, nine hundred fifty".