21501512321591 has 2 divisors, whose sum is σ = 21501512321592. Its totient is φ = 21501512321590.

The previous prime is 21501512321557. The next prime is 21501512321593. The reversal of 21501512321591 is 19512321510512.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21501512321591 is a prime.

Together with 21501512321593, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21501512321593) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10750756160795 + 10750756160796.

It is an arithmetic number, because the mean of its divisors is an integer number (10750756160796).

Almost surely, 2^{21501512321591} is an apocalyptic number.

21501512321591 is a deficient number, since it is larger than the sum of its proper divisors (1).

21501512321591 is an equidigital number, since it uses as much as digits as its factorization.

21501512321591 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 27000, while the sum is 38.

The spelling of 21501512321591 in words is "twenty-one trillion, five hundred one billion, five hundred twelve million, three hundred twenty-one thousand, five hundred ninety-one".