20521406 has 24 divisors (see below), whose sum is σ = 33293304. Its totient is φ = 9480240.

The previous prime is 20521399. The next prime is 20521409. The reversal of 20521406 is 60412502.

It is a happy number.

It is a super-2 number, since 2×20521406² = 842256208433672, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20521409) 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 11 ways as a sum of consecutive naturals, for example, 30716 + ... + 31376.

It is an arithmetic number, because the mean of its divisors is an integer number (1387221).

Almost surely, 2^20521406 is an apocalyptic number.

20521406 is a deficient number, since it is larger than the sum of its proper divisors (12771898).

20521406 is a wasteful number, since it uses less digits than its factorization.

20521406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 744 (or 725 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 20.

The square root of 20521406 is about 4530.0558495453. The cubic root of 20521406 is about 273.7804108470.

Adding to 20521406 its reverse (60412502), we get a palindrome (80933908).

The spelling of 20521406 in words is "twenty million, five hundred twenty-one thousand, four hundred six".