21516919 has 2 divisors, whose sum is σ = 21516920. Its totient is φ = 21516918.

The previous prime is 21516893. The next prime is 21516947. The reversal of 21516919 is 91961512.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21516919 - 2⁷ = 21516791 is a prime.

It is a super-2 number, since 2×21516919² = 925955606505122, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21516959) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10758459 + 10758460.

It is an arithmetic number, because the mean of its divisors is an integer number (10758460).

Almost surely, 2^21516919 is an apocalyptic number.

21516919 is a deficient number, since it is larger than the sum of its proper divisors (1).

21516919 is an equidigital number, since it uses as much as digits as its factorization.

21516919 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4860, while the sum is 34.

The square root of 21516919 is about 4638.6333116555. The cubic root of 21516919 is about 278.1378084241.

The spelling of 21516919 in words is "twenty-one million, five hundred sixteen thousand, nine hundred nineteen".