21418643 has 4 divisors (see below), whose sum is σ = 22545960. Its totient is φ = 20291328.

The previous prime is 21418633. The next prime is 21418693. The reversal of 21418643 is 34681412.

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 21418643 - 2¹⁰ = 21417619 is a prime.

It is a super-2 number, since 2×21418643² = 917516535922898, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21418633) 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, 563630 + ... + 563667.

It is an arithmetic number, because the mean of its divisors is an integer number (5636490).

Almost surely, 2^21418643 is an apocalyptic number.

21418643 is a deficient number, since it is larger than the sum of its proper divisors (1127317).

21418643 is a wasteful number, since it uses less digits than its factorization.

21418643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1127316.

The product of its digits is 4608, while the sum is 29.

The square root of 21418643 is about 4628.0279817650. The cubic root of 21418643 is about 277.7137081686.

The spelling of 21418643 in words is "twenty-one million, four hundred eighteen thousand, six hundred forty-three".