21086723 has 4 divisors (see below), whose sum is σ = 24099120. Its totient is φ = 18074328.

The previous prime is 21086687. The next prime is 21086743. The reversal of 21086723 is 32768012.

It is a happy number.

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 21086723 - 2⁸ = 21086467 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21086743) 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, 1506188 + ... + 1506201.

It is an arithmetic number, because the mean of its divisors is an integer number (6024780).

Almost surely, 2^21086723 is an apocalyptic number.

21086723 is a deficient number, since it is larger than the sum of its proper divisors (3012397).

21086723 is an equidigital number, since it uses as much as digits as its factorization.

21086723 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3012396.

The product of its (nonzero) digits is 4032, while the sum is 29.

The square root of 21086723 is about 4592.0282011329. The cubic root of 21086723 is about 276.2716772845.

The spelling of 21086723 in words is "twenty-one million, eighty-six thousand, seven hundred twenty-three".