21508819 has 8 divisors (see below), whose sum is σ = 21850560. Its totient is φ = 21169896.

The previous prime is 21508801. The next prime is 21508867. The reversal of 21508819 is 91880512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21508819 - 2⁵ = 21508787 is a prime.

It is a super-2 number, since 2×21508819² = 925258589549522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21508889) 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 7 ways as a sum of consecutive naturals, for example, 18592 + ... + 19714.

It is an arithmetic number, because the mean of its divisors is an integer number (2731320).

Almost surely, 2^21508819 is an apocalyptic number.

21508819 is a deficient number, since it is larger than the sum of its proper divisors (341741).

21508819 is a wasteful number, since it uses less digits than its factorization.

21508819 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1409.

The product of its (nonzero) digits is 5760, while the sum is 34.

The square root of 21508819 is about 4637.7601274753. The cubic root of 21508819 is about 278.1029025746.

The spelling of 21508819 in words is "twenty-one million, five hundred eight thousand, eight hundred nineteen".