21547621723 has 2 divisors, whose sum is σ = 21547621724. Its totient is φ = 21547621722.

The previous prime is 21547621721. The next prime is 21547621759. The reversal of 21547621723 is 32712674512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21547621723 - 2¹ = 21547621721 is a prime.

It is a super-4 number, since 4×21547621723⁴ (a number of 42 digits) contains 4444 as substring.

Together with 21547621721, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21547621721) 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 as a sum of consecutive naturals, namely, 10773810861 + 10773810862.

It is an arithmetic number, because the mean of its divisors is an integer number (10773810862).

Almost surely, 2^21547621723 is an apocalyptic number.

21547621723 is a deficient number, since it is larger than the sum of its proper divisors (1).

21547621723 is an equidigital number, since it uses as much as digits as its factorization.

21547621723 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 141120, while the sum is 40.

The spelling of 21547621723 in words is "twenty-one billion, five hundred forty-seven million, six hundred twenty-one thousand, seven hundred twenty-three".