21561719 has 4 divisors (see below), whose sum is σ = 21595896. Its totient is φ = 21527544.

The previous prime is 21561697. The next prime is 21561733. The reversal of 21561719 is 91716512.

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 21561719 - 2¹² = 21557623 is a prime.

It is a super-2 number, since 2×21561719² = 929815452469922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21561769) 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, 16124 + ... + 17409.

It is an arithmetic number, because the mean of its divisors is an integer number (5398974).

Almost surely, 2^21561719 is an apocalyptic number.

21561719 is a deficient number, since it is larger than the sum of its proper divisors (34177).

21561719 is an equidigital number, since it uses as much as digits as its factorization.

21561719 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 34176.

The product of its digits is 3780, while the sum is 32.

The square root of 21561719 is about 4643.4598092371. The cubic root of 21561719 is about 278.3307098928.

The spelling of 21561719 in words is "twenty-one million, five hundred sixty-one thousand, seven hundred nineteen".