21131587 has 2 divisors, whose sum is σ = 21131588. Its totient is φ = 21131586.

The previous prime is 21131581. The next prime is 21131597. The reversal of 21131587 is 78513112.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21131587 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21131581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10565793 + 10565794.

It is an arithmetic number, because the mean of its divisors is an integer number (10565794).

Almost surely, 2^21131587 is an apocalyptic number.

21131587 is a deficient number, since it is larger than the sum of its proper divisors (1).

21131587 is an equidigital number, since it uses as much as digits as its factorization.

21131587 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1680, while the sum is 28.

The square root of 21131587 is about 4596.9105929961. The cubic root of 21131587 is about 276.4674698793.

Adding to 21131587 its reverse (78513112), we get a palindrome (99644699).

The spelling of 21131587 in words is "twenty-one million, one hundred thirty-one thousand, five hundred eighty-seven".