21751187 has 2 divisors, whose sum is σ = 21751188. Its totient is φ = 21751186.

The previous prime is 21751159. The next prime is 21751193. The reversal of 21751187 is 78115712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21751187 - 2¹⁰ = 21750163 is a prime.

It is a super-2 number, since 2×21751187² = 946228271817938, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21751127) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10875593 + 10875594.

It is an arithmetic number, because the mean of its divisors is an integer number (10875594).

Almost surely, 2^21751187 is an apocalyptic number.

21751187 is a deficient number, since it is larger than the sum of its proper divisors (1).

21751187 is an equidigital number, since it uses as much as digits as its factorization.

21751187 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3920, while the sum is 32.

The square root of 21751187 is about 4663.8167845660. The cubic root of 21751187 is about 279.1435864585.

Adding to 21751187 its reverse (78115712), we get a palindrome (99866899).

The spelling of 21751187 in words is "twenty-one million, seven hundred fifty-one thousand, one hundred eighty-seven".