21391277 has 8 divisors (see below), whose sum is σ = 21930264. Its totient is φ = 20857408.

The previous prime is 21391267. The next prime is 21391301. The reversal of 21391277 is 77219312.

It can be written as a sum of positive squares in 4 ways, for example, as 8185321 + 13205956 = 2861^2 + 3634^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21391277 - 2⁴ = 21391261 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21391267) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8003 + ... + 10335.

It is an arithmetic number, because the mean of its divisors is an integer number (2741283).

Almost surely, 2^21391277 is an apocalyptic number.

It is an amenable number.

21391277 is a deficient number, since it is larger than the sum of its proper divisors (538987).

21391277 is a wasteful number, since it uses less digits than its factorization.

21391277 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2559.

The product of its digits is 5292, while the sum is 32.

The square root of 21391277 is about 4625.0704859494. The cubic root of 21391277 is about 277.5953820859.

The spelling of 21391277 in words is "twenty-one million, three hundred ninety-one thousand, two hundred seventy-seven".