21837021 has 8 divisors (see below), whose sum is σ = 29609760. Its totient is φ = 14311152.

The previous prime is 21837019. The next prime is 21837031. The reversal of 21837021 is 12073812.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21837021 - 2¹ = 21837019 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21836982 and 21837000.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21837031) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 61510 + ... + 61863.

It is an arithmetic number, because the mean of its divisors is an integer number (3701220).

Almost surely, 2^21837021 is an apocalyptic number.

It is an amenable number.

21837021 is a deficient number, since it is larger than the sum of its proper divisors (7772739).

21837021 is a wasteful number, since it uses less digits than its factorization.

21837021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 123435.

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 21837021 is about 4673.0098437731. The cubic root of 21837021 is about 279.5102877135.

The spelling of 21837021 in words is "twenty-one million, eight hundred thirty-seven thousand, twenty-one".