21505332377 has 2 divisors, whose sum is σ = 21505332378. Its totient is φ = 21505332376.

The previous prime is 21505332349. The next prime is 21505332379. The reversal of 21505332377 is 77323350512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12306796096 + 9198536281 = 110936^2 + 95909^2 .

It is a cyclic number.

It is not a de Polignac number, because 21505332377 - 2¹⁶ = 21505266841 is a prime.

Together with 21505332379, it forms a pair of twin primes.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21505332377.

It is not a weakly prime, because it can be changed into another prime (21505332379) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10752666188 + 10752666189.

It is an arithmetic number, because the mean of its divisors is an integer number (10752666189).

Almost surely, 2^21505332377 is an apocalyptic number.

It is an amenable number.

21505332377 is a deficient number, since it is larger than the sum of its proper divisors (1).

21505332377 is an equidigital number, since it uses as much as digits as its factorization.

21505332377 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 132300, while the sum is 38.

Adding to 21505332377 its reverse (77323350512), we get a palindrome (98828682889).

The spelling of 21505332377 in words is "twenty-one billion, five hundred five million, three hundred thirty-two thousand, three hundred seventy-seven".