21739973 has 8 divisors (see below), whose sum is σ = 22170456. Its totient is φ = 21312000.

The previous prime is 21739967. The next prime is 21739981. The reversal of 21739973 is 37993712.

It can be written as a sum of positive squares in 4 ways, for example, as 2362369 + 19377604 = 1537^2 + 4402^2 .

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 21739973 - 2¹⁰ = 21738949 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21739973.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21739903) 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, 35873 + ... + 36473.

It is an arithmetic number, because the mean of its divisors is an integer number (2771307).

Almost surely, 2^21739973 is an apocalyptic number.

It is an amenable number.

21739973 is a deficient number, since it is larger than the sum of its proper divisors (430483).

21739973 is an equidigital number, since it uses as much as digits as its factorization.

21739973 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1255.

The product of its digits is 71442, while the sum is 41.

The square root of 21739973 is about 4662.6143953795. The cubic root of 21739973 is about 279.0956066358.

The spelling of 21739973 in words is "twenty-one million, seven hundred thirty-nine thousand, nine hundred seventy-three".