21561743 has 8 divisors (see below), whose sum is σ = 24806400. Its totient is φ = 18358200.

The previous prime is 21561737. The next prime is 21561769. The reversal of 21561743 is 34716512.

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

It is not a de Polignac number, because 21561743 - 2¹⁰ = 21560719 is a prime.

It is a super-2 number, since 2×21561743² = 929817522396098, 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 (21561733) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9143 + ... + 11256.

It is an arithmetic number, because the mean of its divisors is an integer number (3100800).

Almost surely, 2^21561743 is an apocalyptic number.

21561743 is a deficient number, since it is larger than the sum of its proper divisors (3244657).

21561743 is a wasteful number, since it uses less digits than its factorization.

21561743 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20557.

The product of its digits is 5040, while the sum is 29.

The square root of 21561743 is about 4643.4623935163. The cubic root of 21561743 is about 278.3308131612.

The spelling of 21561743 in words is "twenty-one million, five hundred sixty-one thousand, seven hundred forty-three".