21334487561 has 2 divisors, whose sum is σ = 21334487562. Its totient is φ = 21334487560.

The previous prime is 21334487519. The next prime is 21334487621. The reversal of 21334487561 is 16578443312.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20773745161 + 560742400 = 144131^2 + 23680^2 .

It is a cyclic number.

It is not a de Polignac number, because 21334487561 - 2¹⁸ = 21334225417 is a prime.

It is not a weakly prime, because it can be changed into another prime (21334487861) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10667243780 + 10667243781.

It is an arithmetic number, because the mean of its divisors is an integer number (10667243781).

Almost surely, 2^21334487561 is an apocalyptic number.

It is an amenable number.

21334487561 is a deficient number, since it is larger than the sum of its proper divisors (1).

21334487561 is an equidigital number, since it uses as much as digits as its factorization.

21334487561 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 483840, while the sum is 44.

The spelling of 21334487561 in words is "twenty-one billion, three hundred thirty-four million, four hundred eighty-seven thousand, five hundred sixty-one".