21371723 has 4 divisors (see below), whose sum is σ = 21392928. Its totient is φ = 21350520.

The previous prime is 21371717. The next prime is 21371759. The reversal of 21371723 is 32717312.

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 21371723 - 2¹⁸ = 21109579 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21371692 and 21371701.

It is not an unprimeable number, because it can be changed into a prime (21371423) 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, 9011 + ... + 11132.

It is an arithmetic number, because the mean of its divisors is an integer number (5348232).

Almost surely, 2^21371723 is an apocalyptic number.

21371723 is a deficient number, since it is larger than the sum of its proper divisors (21205).

21371723 is a wasteful number, since it uses less digits than its factorization.

21371723 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21204.

The product of its digits is 1764, while the sum is 26.

The square root of 21371723 is about 4622.9560889111. The cubic root of 21371723 is about 277.5107719759.

The spelling of 21371723 in words is "twenty-one million, three hundred seventy-one thousand, seven hundred twenty-three".