21121002187 has 2 divisors, whose sum is σ = 21121002188. Its totient is φ = 21121002186.

The previous prime is 21121002179. The next prime is 21121002211. The reversal of 21121002187 is 78120012112.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21121002187 - 2³ = 21121002179 is a prime.

It is not a weakly prime, because it can be changed into another prime (21121002107) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10560501093 + 10560501094.

It is an arithmetic number, because the mean of its divisors is an integer number (10560501094).

Almost surely, 2^21121002187 is an apocalyptic number.

21121002187 is a deficient number, since it is larger than the sum of its proper divisors (1).

21121002187 is an equidigital number, since it uses as much as digits as its factorization.

21121002187 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 448, while the sum is 25.

Adding to 21121002187 its reverse (78120012112), we get a palindrome (99241014299).

The spelling of 21121002187 in words is "twenty-one billion, one hundred twenty-one million, two thousand, one hundred eighty-seven".