21361742657 has 2 divisors, whose sum is σ = 21361742658. Its totient is φ = 21361742656.

The previous prime is 21361742653. The next prime is 21361742681. The reversal of 21361742657 is 75624716312.

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., 16544133376 + 4817609281 = 128624^2 + 69409^2 .

It is a cyclic number.

It is not a de Polignac number, because 21361742657 - 2² = 21361742653 is a prime.

It is not a weakly prime, because it can be changed into another prime (21361742653) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10680871328 + 10680871329.

It is an arithmetic number, because the mean of its divisors is an integer number (10680871329).

Almost surely, 2^21361742657 is an apocalyptic number.

It is an amenable number.

21361742657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21361742657 is an equidigital number, since it uses as much as digits as its factorization.

21361742657 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 423360, while the sum is 44.

The spelling of 21361742657 in words is "twenty-one billion, three hundred sixty-one million, seven hundred forty-two thousand, six hundred fifty-seven".