21151787 has 2 divisors, whose sum is σ = 21151788. Its totient is φ = 21151786.

The previous prime is 21151783. The next prime is 21151799. The reversal of 21151787 is 78715112.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21151787 - 2² = 21151783 is a prime.

It is not a weakly prime, because it can be changed into another prime (21151783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10575893 + 10575894.

It is an arithmetic number, because the mean of its divisors is an integer number (10575894).

Almost surely, 2^21151787 is an apocalyptic number.

21151787 is a deficient number, since it is larger than the sum of its proper divisors (1).

21151787 is an equidigital number, since it uses as much as digits as its factorization.

21151787 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21151787 is about 4599.1071959675. The cubic root of 21151787 is about 276.5555349539. Note that the first 4 decimals are identical.

Adding to 21151787 its reverse (78715112), we get a palindrome (99866899).

The spelling of 21151787 in words is "twenty-one million, one hundred fifty-one thousand, seven hundred eighty-seven".