21523619 has 4 divisors (see below), whose sum is σ = 23179296. Its totient is φ = 19867944.

The previous prime is 21523609. The next prime is 21523631. The reversal of 21523619 is 91632512.

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 21523619 - 2¹² = 21519523 is a prime.

It is a super-2 number, since 2×21523619² = 926532349714322, 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 = 21523591 and 21523600.

It is not an unprimeable number, because it can be changed into a prime (21523609) 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, 827819 + ... + 827844.

It is an arithmetic number, because the mean of its divisors is an integer number (5794824).

Almost surely, 2^21523619 is an apocalyptic number.

21523619 is a deficient number, since it is larger than the sum of its proper divisors (1655677).

21523619 is a wasteful number, since it uses less digits than its factorization.

21523619 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1655676.

The product of its digits is 3240, while the sum is 29.

The square root of 21523619 is about 4639.3554509220. The cubic root of 21523619 is about 278.1666745446.

The spelling of 21523619 in words is "twenty-one million, five hundred twenty-three thousand, six hundred nineteen".