21031685723 has 2 divisors, whose sum is σ = 21031685724. Its totient is φ = 21031685722.

The previous prime is 21031685699. The next prime is 21031685749. The reversal of 21031685723 is 32758613012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21031685723 - 2¹⁰ = 21031684699 is a prime.

It is not a weakly prime, because it can be changed into another prime (21031385723) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10515842861 + 10515842862.

It is an arithmetic number, because the mean of its divisors is an integer number (10515842862).

Almost surely, 2^21031685723 is an apocalyptic number.

21031685723 is a deficient number, since it is larger than the sum of its proper divisors (1).

21031685723 is an equidigital number, since it uses as much as digits as its factorization.

21031685723 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 60480, while the sum is 38.

The spelling of 21031685723 in words is "twenty-one billion, thirty-one million, six hundred eighty-five thousand, seven hundred twenty-three".