21623871 has 4 divisors (see below), whose sum is σ = 28831832. Its totient is φ = 14415912.

The previous prime is 21623867. The next prime is 21623891. The reversal of 21623871 is 17832612.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21623871 - 2² = 21623867 is a prime.

It is a super-3 number, since 3×21623871³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21623891) 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, 3603976 + ... + 3603981.

It is an arithmetic number, because the mean of its divisors is an integer number (7207958).

Almost surely, 2^21623871 is an apocalyptic number.

21623871 is a deficient number, since it is larger than the sum of its proper divisors (7207961).

21623871 is an equidigital number, since it uses as much as digits as its factorization.

21623871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7207960.

The product of its digits is 4032, while the sum is 30.

The square root of 21623871 is about 4650.1474170181. The cubic root of 21623871 is about 278.5978842537.

The spelling of 21623871 in words is "twenty-one million, six hundred twenty-three thousand, eight hundred seventy-one".