21377 has 2 divisors, whose sum is σ = 21378. Its totient is φ = 21376.

The previous prime is 21347. The next prime is 21379. The reversal of 21377 is 77312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13456 + 7921 = 116^2 + 89^2 .

It is a cyclic number.

It is not a de Polignac number, because 21377 - 2⁶ = 21313 is a prime.

It is a super-2 number, since 2×21377² = 913952258, which contains 22 as substring.

Together with 21379, it forms a pair of twin primes.

It is a Chen prime.

It is a nialpdrome in base 13.

It is not a weakly prime, because it can be changed into another prime (21379) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10688 + 10689.

It is an arithmetic number, because the mean of its divisors is an integer number (10689).

2²¹³⁷⁷ is an apocalyptic number.

It is an amenable number.

21377 is a deficient number, since it is larger than the sum of its proper divisors (1).

21377 is an equidigital number, since it uses as much as digits as its factorization.

21377 is an evil number, because the sum of its binary digits is even.

The product of its digits is 294, while the sum is 20.

The square root of 21377 is about 146.2087548678. The cubic root of 21377 is about 27.7533610625.

Adding to 21377 its reverse (77312), we get a palindrome (98689).

The spelling of 21377 in words is "twenty-one thousand, three hundred seventy-seven", and thus it is an iban number.