21746021 has 4 divisors (see below), whose sum is σ = 23722944. Its totient is φ = 19769100.

The previous prime is 21745991. The next prime is 21746029. The reversal of 21746021 is 12064712.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21746021 - 2⁶ = 21745957 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21746029) 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 3 ways as a sum of consecutive naturals, for example, 988445 + ... + 988466.

It is an arithmetic number, because the mean of its divisors is an integer number (5930736).

Almost surely, 2^21746021 is an apocalyptic number.

It is an amenable number.

21746021 is a deficient number, since it is larger than the sum of its proper divisors (1976923).

21746021 is a wasteful number, since it uses less digits than its factorization.

21746021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1976922.

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 21746021 is about 4663.2629134545. The cubic root of 21746021 is about 279.1214854433.

The spelling of 21746021 in words is "twenty-one million, seven hundred forty-six thousand, twenty-one".