20921005 has 16 divisors (see below), whose sum is σ = 29361024. Its totient is φ = 14011200.

The previous prime is 20920993. The next prime is 20921009. The reversal of 20921005 is 50012902.

It is not a de Polignac number, because 20921005 - 2¹¹ = 20918957 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20921009) 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, 5446 + ... + 8455.

It is an arithmetic number, because the mean of its divisors is an integer number (1835064).

Almost surely, 2^20921005 is an apocalyptic number.

It is an amenable number.

20921005 is a deficient number, since it is larger than the sum of its proper divisors (8440019).

20921005 is a wasteful number, since it uses less digits than its factorization.

20921005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13956.

The product of its (nonzero) digits is 180, while the sum is 19.

The square root of 20921005 is about 4573.9485130465. The cubic root of 20921005 is about 275.5460445240.

Adding to 20921005 its reverse (50012902), we get a palindrome (70933907).

The spelling of 20921005 in words is "twenty million, nine hundred twenty-one thousand, five".