21491516741 has 4 divisors (see below), whose sum is σ = 21540472800. Its totient is φ = 21442560684.

The previous prime is 21491516663. The next prime is 21491516743. The reversal of 21491516741 is 14761519412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21491516741 is a prime.

It is a super-2 number, since 2×21491516741² (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 (21491516743) 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, 24477371 + ... + 24478248.

It is an arithmetic number, because the mean of its divisors is an integer number (5385118200).

Almost surely, 2^21491516741 is an apocalyptic number.

It is an amenable number.

21491516741 is a deficient number, since it is larger than the sum of its proper divisors (48956059).

21491516741 is an equidigital number, since it uses as much as digits as its factorization.

21491516741 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 48956058.

The product of its digits is 60480, while the sum is 41.

The spelling of 21491516741 in words is "twenty-one billion, four hundred ninety-one million, five hundred sixteen thousand, seven hundred forty-one".