21087331 has 2 divisors, whose sum is σ = 21087332. Its totient is φ = 21087330.

The previous prime is 21087289. The next prime is 21087337. The reversal of 21087331 is 13378012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21087331 - 2⁷ = 21087203 is a prime.

It is a super-2 number, since 2×21087331² = 889351057407122, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21087296 and 21087305.

It is not a weakly prime, because it can be changed into another prime (21087337) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10543665 + 10543666.

It is an arithmetic number, because the mean of its divisors is an integer number (10543666).

Almost surely, 2^21087331 is an apocalyptic number.

21087331 is a deficient number, since it is larger than the sum of its proper divisors (1).

21087331 is an equidigital number, since it uses as much as digits as its factorization.

21087331 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1008, while the sum is 25.

The square root of 21087331 is about 4592.0944023397. The cubic root of 21087331 is about 276.2743325345.

The spelling of 21087331 in words is "twenty-one million, eighty-seven thousand, three hundred thirty-one".