21515402165723 has 2 divisors, whose sum is σ = 21515402165724. Its totient is φ = 21515402165722.

The previous prime is 21515402165713. The next prime is 21515402165729. The reversal of 21515402165723 is 32756120451512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21515402165723 - 2⁶ = 21515402165659 is a prime.

It is a super-2 number, since 2×21515402165723² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21515402165729) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10757701082861 + 10757701082862.

It is an arithmetic number, because the mean of its divisors is an integer number (10757701082862).

Almost surely, 2^{21515402165723} is an apocalyptic number.

21515402165723 is a deficient number, since it is larger than the sum of its proper divisors (1).

21515402165723 is an equidigital number, since it uses as much as digits as its factorization.

21515402165723 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 504000, while the sum is 44.

The spelling of 21515402165723 in words is "twenty-one trillion, five hundred fifteen billion, four hundred two million, one hundred sixty-five thousand, seven hundred twenty-three".