21684419 has 4 divisors (see below), whose sum is σ = 21706920. Its totient is φ = 21661920.

The previous prime is 21684413. The next prime is 21684461. The reversal of 21684419 is 91448612.

It is a happy number.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21684419 is a prime.

It is a super-2 number, since 2×21684419² = 940428054735122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21684413) 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 in 3 ways as a sum of consecutive naturals, for example, 9737 + ... + 11754.

It is an arithmetic number, because the mean of its divisors is an integer number (5426730).

Almost surely, 2^21684419 is an apocalyptic number.

21684419 is a deficient number, since it is larger than the sum of its proper divisors (22501).

21684419 is a wasteful number, since it uses less digits than its factorization.

21684419 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22500.

The product of its digits is 13824, while the sum is 35.

The square root of 21684419 is about 4656.6531973081. The cubic root of 21684419 is about 278.8576716104.

The spelling of 21684419 in words is "twenty-one million, six hundred eighty-four thousand, four hundred nineteen".