21605665451507 has 2 divisors, whose sum is σ = 21605665451508. Its totient is φ = 21605665451506.

The previous prime is 21605665451501. The next prime is 21605665451527. The reversal of 21605665451507 is 70515456650612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21605665451507 - 2¹² = 21605665447411 is a prime.

It is not a weakly prime, because it can be changed into another prime (21605665451501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10802832725753 + 10802832725754.

It is an arithmetic number, because the mean of its divisors is an integer number (10802832725754).

Almost surely, 2^{21605665451507} is an apocalyptic number.

21605665451507 is a deficient number, since it is larger than the sum of its proper divisors (1).

21605665451507 is an equidigital number, since it uses as much as digits as its factorization.

21605665451507 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7560000, while the sum is 53.

The spelling of 21605665451507 in words is "twenty-one trillion, six hundred five billion, six hundred sixty-five million, four hundred fifty-one thousand, five hundred seven".