21619643 has 4 divisors (see below), whose sum is σ = 21775320. Its totient is φ = 21463968.

The previous prime is 21619621. The next prime is 21619649. The reversal of 21619643 is 34691612.

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 21619643 - 2⁶ = 21619579 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21619649) 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, 77630 + ... + 77907.

It is an arithmetic number, because the mean of its divisors is an integer number (5443830).

Almost surely, 2^21619643 is an apocalyptic number.

21619643 is a deficient number, since it is larger than the sum of its proper divisors (155677).

21619643 is a wasteful number, since it uses less digits than its factorization.

21619643 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 155676.

The product of its digits is 7776, while the sum is 32.

The square root of 21619643 is about 4649.6927855505. The cubic root of 21619643 is about 278.5797254847.

The spelling of 21619643 in words is "twenty-one million, six hundred nineteen thousand, six hundred forty-three".