21723989 has 8 divisors (see below), whose sum is σ = 25074048. Its totient is φ = 18435600.

The previous prime is 21723979. The next prime is 21724007. The reversal of 21723989 is 98932712.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21723989 - 2⁸ = 21723733 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21723959) 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, 14657 + ... + 16070.

It is an arithmetic number, because the mean of its divisors is an integer number (3134256).

Almost surely, 2^21723989 is an apocalyptic number.

It is an amenable number.

21723989 is a deficient number, since it is larger than the sum of its proper divisors (3350059).

21723989 is a wasteful number, since it uses less digits than its factorization.

21723989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 30835.

The product of its digits is 54432, while the sum is 41.

The square root of 21723989 is about 4660.9000203823. The cubic root of 21723989 is about 279.0271895326.

The spelling of 21723989 in words is "twenty-one million, seven hundred twenty-three thousand, nine hundred eighty-nine".