21491003783 has 4 divisors (see below), whose sum is σ = 21495117408. Its totient is φ = 21486890160.

The previous prime is 21491003771. The next prime is 21491003801. The reversal of 21491003783 is 38730019412.

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 21491003783 - 2⁴ = 21491003767 is a prime.

It is a super-2 number, since 2×21491003783² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21491003383) 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, 2048966 + ... + 2059427.

It is an arithmetic number, because the mean of its divisors is an integer number (5373779352).

Almost surely, 2^21491003783 is an apocalyptic number.

21491003783 is a deficient number, since it is larger than the sum of its proper divisors (4113625).

21491003783 is an equidigital number, since it uses as much as digits as its factorization.

21491003783 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4113624.

The product of its (nonzero) digits is 36288, while the sum is 38.

The spelling of 21491003783 in words is "twenty-one billion, four hundred ninety-one million, three thousand, seven hundred eighty-three".