21379277 has 2 divisors, whose sum is σ = 21379278. Its totient is φ = 21379276.

The previous prime is 21379271. The next prime is 21379279. The reversal of 21379277 is 77297312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21058921 + 320356 = 4589^2 + 566^2 .

It is a cyclic number.

It is not a de Polignac number, because 21379277 - 2⁸ = 21379021 is a prime.

Together with 21379279, 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 21379277.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21379271) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10689638 + 10689639.

It is an arithmetic number, because the mean of its divisors is an integer number (10689639).

Almost surely, 2^21379277 is an apocalyptic number.

It is an amenable number.

21379277 is a deficient number, since it is larger than the sum of its proper divisors (1).

21379277 is an equidigital number, since it uses as much as digits as its factorization.

21379277 is an evil number, because the sum of its binary digits is even.

The product of its digits is 37044, while the sum is 38.

The square root of 21379277 is about 4623.7730264363. The cubic root of 21379277 is about 277.5434642305.

The spelling of 21379277 in words is "twenty-one million, three hundred seventy-nine thousand, two hundred seventy-seven".