21087771 has 4 divisors (see below), whose sum is σ = 28117032. Its totient is φ = 14058512.

The previous prime is 21087763. The next prime is 21087779. The reversal of 21087771 is 17778012.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21087763) and next prime (21087779).

It is a cyclic number.

It is not a de Polignac number, because 21087771 - 2³ = 21087763 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21087779) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3514626 + ... + 3514631.

It is an arithmetic number, because the mean of its divisors is an integer number (7029258).

Almost surely, 2^21087771 is an apocalyptic number.

21087771 is a deficient number, since it is larger than the sum of its proper divisors (7029261).

21087771 is an equidigital number, since it uses as much as digits as its factorization.

21087771 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7029260.

The product of its (nonzero) digits is 5488, while the sum is 33.

The square root of 21087771 is about 4592.1423105126. The cubic root of 21087771 is about 276.2762540652.

The spelling of 21087771 in words is "twenty-one million, eighty-seven thousand, seven hundred seventy-one".