21081019 has 2 divisors, whose sum is σ = 21081020. Its totient is φ = 21081018.

The previous prime is 21081017. The next prime is 21081029. The reversal of 21081019 is 91018012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21081019 - 2¹ = 21081017 is a prime.

It is a super-2 number, since 2×21081019² = 888818724156722, which contains 22 as substring.

Together with 21081017, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21081017) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10540509 + 10540510.

It is an arithmetic number, because the mean of its divisors is an integer number (10540510).

Almost surely, 2^21081019 is an apocalyptic number.

21081019 is a deficient number, since it is larger than the sum of its proper divisors (1).

21081019 is an equidigital number, since it uses as much as digits as its factorization.

21081019 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 144, while the sum is 22.

The square root of 21081019 is about 4591.4070828015. The cubic root of 21081019 is about 276.2467643609.

The spelling of 21081019 in words is "twenty-one million, eighty-one thousand, nineteen".