21385021 has 8 divisors (see below), whose sum is σ = 24939200. Its totient is φ = 18329724.

The previous prime is 21384991. The next prime is 21385057. The reversal of 21385021 is 12058312.

It is not a de Polignac number, because 21385021 - 2⁷ = 21384893 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21384983 and 21385001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21385321) 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, 30831 + ... + 31516.

It is an arithmetic number, because the mean of its divisors is an integer number (3117400).

Almost surely, 2^21385021 is an apocalyptic number.

It is an amenable number.

21385021 is a deficient number, since it is larger than the sum of its proper divisors (3554179).

21385021 is an frugal number, since it uses more digits than its factorization.

21385021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 62368 (or 62354 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 21385021 is about 4624.3941224770. The cubic root of 21385021 is about 277.5683180007.

The spelling of 21385021 in words is "twenty-one million, three hundred eighty-five thousand, twenty-one".