21723705 has 48 divisors (see below), whose sum is σ = 40519440. Its totient is φ = 10727424.

The previous prime is 21723701. The next prime is 21723719. The reversal of 21723705 is 50732712.

It can be written as a sum of positive squares in 8 ways, for example, as 17424 + 21706281 = 132^2 + 4659^2 .

It is not a de Polignac number, because 21723705 - 2² = 21723701 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21723701) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 55651 + ... + 56039.

It is an arithmetic number, because the mean of its divisors is an integer number (844155).

Almost surely, 2^21723705 is an apocalyptic number.

It is an amenable number.

21723705 is a deficient number, since it is larger than the sum of its proper divisors (18795735).

21723705 is a wasteful number, since it uses less digits than its factorization.

21723705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 490 (or 487 counting only the distinct ones).

The product of its (nonzero) digits is 2940, while the sum is 27.

The square root of 21723705 is about 4660.8695540639. The cubic root of 21723705 is about 279.0259736100.

The spelling of 21723705 in words is "twenty-one million, seven hundred twenty-three thousand, seven hundred five".