21510402317 has 2 divisors, whose sum is σ = 21510402318. Its totient is φ = 21510402316.

The previous prime is 21510402283. The next prime is 21510402337. The reversal of 21510402317 is 71320401512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18056371876 + 3454030441 = 134374^2 + 58771^2 .

It is a cyclic number.

It is not a de Polignac number, because 21510402317 - 2¹⁶ = 21510336781 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21510402337) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10755201158 + 10755201159.

It is an arithmetic number, because the mean of its divisors is an integer number (10755201159).

Almost surely, 2^21510402317 is an apocalyptic number.

It is an amenable number.

21510402317 is a deficient number, since it is larger than the sum of its proper divisors (1).

21510402317 is an equidigital number, since it uses as much as digits as its factorization.

21510402317 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1680, while the sum is 26.

Adding to 21510402317 its reverse (71320401512), we get a palindrome (92830803829).

The spelling of 21510402317 in words is "twenty-one billion, five hundred ten million, four hundred two thousand, three hundred seventeen".