21003455991 has 24 divisors (see below), whose sum is σ = 32713148160. Its totient is φ = 11951737392.

The previous prime is 21003455983. The next prime is 21003456029. The reversal of 21003455991 is 19955430012.

It is not a de Polignac number, because 21003455991 - 2³ = 21003455983 is a prime.

It is a super-2 number, since 2×21003455991² (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 (21003455911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 263781 + ... + 334046.

It is an arithmetic number, because the mean of its divisors is an integer number (1363047840).

Almost surely, 2^21003455991 is an apocalyptic number.

21003455991 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

21003455991 is a deficient number, since it is larger than the sum of its proper divisors (11709692169).

21003455991 is a wasteful number, since it uses less digits than its factorization.

21003455991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 598083 (or 598076 counting only the distinct ones).

The product of its (nonzero) digits is 48600, while the sum is 39.

The spelling of 21003455991 in words is "twenty-one billion, three million, four hundred fifty-five thousand, nine hundred ninety-one".