21842521817 has 2 divisors, whose sum is σ = 21842521818. Its totient is φ = 21842521816.

The previous prime is 21842521807. The next prime is 21842521853. The reversal of 21842521817 is 71812524812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21839223961 + 3297856 = 147781^2 + 1816^2 .

It is a cyclic number.

It is not a de Polignac number, because 21842521817 - 2¹⁰ = 21842520793 is a prime.

It is a super-2 number, since 2×21842521817² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21842521807) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10921260908 + 10921260909.

It is an arithmetic number, because the mean of its divisors is an integer number (10921260909).

Almost surely, 2^21842521817 is an apocalyptic number.

It is an amenable number.

21842521817 is a deficient number, since it is larger than the sum of its proper divisors (1).

21842521817 is an equidigital number, since it uses as much as digits as its factorization.

21842521817 is an evil number, because the sum of its binary digits is even.

The product of its digits is 71680, while the sum is 41.

The spelling of 21842521817 in words is "twenty-one billion, eight hundred forty-two million, five hundred twenty-one thousand, eight hundred seventeen".