21234556517 has 2 divisors, whose sum is σ = 21234556518. Its totient is φ = 21234556516.

The previous prime is 21234556507. The next prime is 21234556543. The reversal of 21234556517 is 71565543212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11861605921 + 9372950596 = 108911^2 + 96814^2 .

It is a cyclic number.

It is not a de Polignac number, because 21234556517 - 2⁸ = 21234556261 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21234556507) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10617278258 + 10617278259.

It is an arithmetic number, because the mean of its divisors is an integer number (10617278259).

Almost surely, 2^21234556517 is an apocalyptic number.

It is an amenable number.

21234556517 is a deficient number, since it is larger than the sum of its proper divisors (1).

21234556517 is an equidigital number, since it uses as much as digits as its factorization.

21234556517 is an evil number, because the sum of its binary digits is even.

The product of its digits is 252000, while the sum is 41.

It can be divided in two parts, 212345 and 56517, that added together give a palindrome (268862).

The spelling of 21234556517 in words is "twenty-one billion, two hundred thirty-four million, five hundred fifty-six thousand, five hundred seventeen".