21723417 has 8 divisors (see below), whose sum is σ = 32182880. Its totient is φ = 14482260.

The previous prime is 21723409. The next prime is 21723419. The reversal of 21723417 is 71432712.

It is a happy number.

It is not a de Polignac number, because 21723417 - 2³ = 21723409 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 804571 = 21723417 / (2 + 1 + 7 + 2 + 3 + 4 + 1 + 7).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21723419) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 402259 + ... + 402312.

It is an arithmetic number, because the mean of its divisors is an integer number (4022860).

Almost surely, 2^21723417 is an apocalyptic number.

21723417 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21723417 is a deficient number, since it is larger than the sum of its proper divisors (10459463).

21723417 is an equidigital number, since it uses as much as digits as its factorization.

21723417 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 804580 (or 804574 counting only the distinct ones).

The product of its digits is 2352, while the sum is 27.

The square root of 21723417 is about 4660.8386584391. The cubic root of 21723417 is about 279.0247405509.

The spelling of 21723417 in words is "twenty-one million, seven hundred twenty-three thousand, four hundred seventeen".