21087277 has 2 divisors, whose sum is σ = 21087278. Its totient is φ = 21087276.

The previous prime is 21087221. The next prime is 21087281. The reversal of 21087277 is 77278012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15792676 + 5294601 = 3974^2 + 2301^2 .

It is a cyclic number.

It is not a de Polignac number, because 21087277 - 2⁷ = 21087149 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21087377) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10543638 + 10543639.

It is an arithmetic number, because the mean of its divisors is an integer number (10543639).

Almost surely, 2^21087277 is an apocalyptic number.

It is an amenable number.

21087277 is a deficient number, since it is larger than the sum of its proper divisors (1).

21087277 is an equidigital number, since it uses as much as digits as its factorization.

21087277 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 10976, while the sum is 34.

The square root of 21087277 is about 4592.0885226659. The cubic root of 21087277 is about 276.2740967085.

The spelling of 21087277 in words is "twenty-one million, eighty-seven thousand, two hundred seventy-seven".