21821519 has 4 divisors (see below), whose sum is σ = 22970040. Its totient is φ = 20673000.

The previous prime is 21821507. The next prime is 21821533. The reversal of 21821519 is 91512812.

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 21821519 - 2⁸ = 21821263 is a prime.

It is a super-2 number, since 2×21821519² = 952357382934722, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21821491 and 21821500.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21821539) 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, 574232 + ... + 574269.

It is an arithmetic number, because the mean of its divisors is an integer number (5742510).

Almost surely, 2^21821519 is an apocalyptic number.

21821519 is a deficient number, since it is larger than the sum of its proper divisors (1148521).

21821519 is a wasteful number, since it uses less digits than its factorization.

21821519 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1148520.

The product of its digits is 1440, while the sum is 29.

The square root of 21821519 is about 4671.3508752822. The cubic root of 21821519 is about 279.4441310370. Note that the first 3 decimals are identical.

The spelling of 21821519 in words is "twenty-one million, eight hundred twenty-one thousand, five hundred nineteen".