21662819 has 2 divisors, whose sum is σ = 21662820. Its totient is φ = 21662818.

The previous prime is 21662813. The next prime is 21662821. The reversal of 21662819 is 91826612.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21662819 is a prime.

It is a super-2 number, since 2×21662819² = 938555454053522, which contains 22 as substring.

Together with 21662821, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21662813) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10831409 + 10831410.

It is an arithmetic number, because the mean of its divisors is an integer number (10831410).

Almost surely, 2^21662819 is an apocalyptic number.

21662819 is a deficient number, since it is larger than the sum of its proper divisors (1).

21662819 is an equidigital number, since it uses as much as digits as its factorization.

21662819 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10368, while the sum is 35.

The square root of 21662819 is about 4654.3333572059. Note that the first 4 decimals coincide. The cubic root of 21662819 is about 278.7650501637.

The spelling of 21662819 in words is "twenty-one million, six hundred sixty-two thousand, eight hundred nineteen".