21131087 has 2 divisors, whose sum is σ = 21131088. Its totient is φ = 21131086.

The previous prime is 21131083. The next prime is 21131137. The reversal of 21131087 is 78013112.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21131087 - 2² = 21131083 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21131081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10565543 + 10565544.

It is an arithmetic number, because the mean of its divisors is an integer number (10565544).

Almost surely, 2^21131087 is an apocalyptic number.

21131087 is a deficient number, since it is larger than the sum of its proper divisors (1).

21131087 is an equidigital number, since it uses as much as digits as its factorization.

21131087 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 336, while the sum is 23.

The square root of 21131087 is about 4596.8562083232. The cubic root of 21131087 is about 276.4652893391.

Adding to 21131087 its reverse (78013112), we get a palindrome (99144199).

The spelling of 21131087 in words is "twenty-one million, one hundred thirty-one thousand, eighty-seven".