21161887 has 2 divisors, whose sum is σ = 21161888. Its totient is φ = 21161886.

The previous prime is 21161869. The next prime is 21161911. The reversal of 21161887 is 78816112.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21161887 is a prime.

It is a super-2 number, since 2×21161887² = 895650922801538, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21161857) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10580943 + 10580944.

It is an arithmetic number, because the mean of its divisors is an integer number (10580944).

Almost surely, 2^21161887 is an apocalyptic number.

21161887 is a deficient number, since it is larger than the sum of its proper divisors (1).

21161887 is an equidigital number, since it uses as much as digits as its factorization.

21161887 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5376, while the sum is 34.

The square root of 21161887 is about 4600.2051041231. The cubic root of 21161887 is about 276.5995464667.

Adding to 21161887 its reverse (78816112), we get a palindrome (99977999).

The spelling of 21161887 in words is "twenty-one million, one hundred sixty-one thousand, eight hundred eighty-seven".