21181901990 has 8 divisors (see below), whose sum is σ = 38127423600. Its totient is φ = 8472760792.

The previous prime is 21181901987. The next prime is 21181901999. The reversal of 21181901990 is 9910918112.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21181901999) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1059095090 + ... + 1059095109.

It is an arithmetic number, because the mean of its divisors is an integer number (4765927950).

Almost surely, 2^21181901990 is an apocalyptic number.

21181901990 is a deficient number, since it is larger than the sum of its proper divisors (16945521610).

21181901990 is a wasteful number, since it uses less digits than its factorization.

21181901990 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2118190206.

The product of its (nonzero) digits is 11664, while the sum is 41.

The spelling of 21181901990 in words is "twenty-one billion, one hundred eighty-one million, nine hundred one thousand, nine hundred ninety".