21020406 has 32 divisors (see below), whose sum is σ = 46061568. Its totient is φ = 6342240.

The previous prime is 21020369. The next prime is 21020407. The reversal of 21020406 is 60402012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020407) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18795 + ... + 19881.

It is an arithmetic number, because the mean of its divisors is an integer number (1439424).

Almost surely, 2^21020406 is an apocalyptic number.

21020406 is an abundant number, since it is smaller than the sum of its proper divisors (25041162).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21020406 is a wasteful number, since it uses less digits than its factorization.

21020406 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1396.

The product of its (nonzero) digits is 96, while the sum is 15.

The square root of 21020406 is about 4584.8016314776. The cubic root of 21020406 is about 275.9817515765.

Adding to 21020406 its reverse (60402012), we get a palindrome (81422418).

The spelling of 21020406 in words is "twenty-one million, twenty thousand, four hundred six".