21387277 has 2 divisors, whose sum is σ = 21387278. Its totient is φ = 21387276.

The previous prime is 21387257. The next prime is 21387287. The reversal of 21387277 is 77278312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18887716 + 2499561 = 4346^2 + 1581^2 .

It is a cyclic number.

It is not a de Polignac number, because 21387277 - 2²³ = 12998669 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21387227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10693638 + 10693639.

It is an arithmetic number, because the mean of its divisors is an integer number (10693639).

Almost surely, 2^21387277 is an apocalyptic number.

It is an amenable number.

21387277 is a deficient number, since it is larger than the sum of its proper divisors (1).

21387277 is an equidigital number, since it uses as much as digits as its factorization.

21387277 is an evil number, because the sum of its binary digits is even.

The product of its digits is 32928, while the sum is 37.

The square root of 21387277 is about 4624.6380398903. The cubic root of 21387277 is about 277.5780782920.

The spelling of 21387277 in words is "twenty-one million, three hundred eighty-seven thousand, two hundred seventy-seven".