21321578723 has 2 divisors, whose sum is σ = 21321578724. Its totient is φ = 21321578722.

The previous prime is 21321578683. The next prime is 21321578731. The reversal of 21321578723 is 32787512312.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21321578723 - 2¹⁸ = 21321316579 is a prime.

It is not a weakly prime, because it can be changed into another prime (21321578743) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10660789361 + 10660789362.

It is an arithmetic number, because the mean of its divisors is an integer number (10660789362).

Almost surely, 2^21321578723 is an apocalyptic number.

21321578723 is a deficient number, since it is larger than the sum of its proper divisors (1).

21321578723 is an equidigital number, since it uses as much as digits as its factorization.

21321578723 is an evil number, because the sum of its binary digits is even.

The product of its digits is 141120, while the sum is 41.

The spelling of 21321578723 in words is "twenty-one billion, three hundred twenty-one million, five hundred seventy-eight thousand, seven hundred twenty-three".