21366019 has 4 divisors (see below), whose sum is σ = 21489696. Its totient is φ = 21242344.

The previous prime is 21366017. The next prime is 21366041. The reversal of 21366019 is 91066312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21366019 - 2¹ = 21366017 is a prime.

It is a super-2 number, since 2×21366019² = 913013535816722, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21366017) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 61579 + ... + 61924.

It is an arithmetic number, because the mean of its divisors is an integer number (5372424).

Almost surely, 2^21366019 is an apocalyptic number.

21366019 is a deficient number, since it is larger than the sum of its proper divisors (123677).

21366019 is a wasteful number, since it uses less digits than its factorization.

21366019 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 123676.

The product of its (nonzero) digits is 1944, while the sum is 28.

The square root of 21366019 is about 4622.3391264597. The cubic root of 21366019 is about 277.4860810593.

The spelling of 21366019 in words is "twenty-one million, three hundred sixty-six thousand, nineteen".