20731421 has 4 divisors (see below), whose sum is σ = 20742144. Its totient is φ = 20720700.

The previous prime is 20731411. The next prime is 20731423. The reversal of 20731421 is 12413702.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20731421 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 20731393 and 20731402.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20731423) 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 3 ways as a sum of consecutive naturals, for example, 1565 + ... + 6626.

It is an arithmetic number, because the mean of its divisors is an integer number (5185536).

Almost surely, 2^20731421 is an apocalyptic number.

It is an amenable number.

20731421 is a deficient number, since it is larger than the sum of its proper divisors (10723).

20731421 is an equidigital number, since it uses as much as digits as its factorization.

20731421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10722.

The product of its (nonzero) digits is 336, while the sum is 20.

The square root of 20731421 is about 4553.1770226953. The cubic root of 20731421 is about 274.7111943224.

The spelling of 20731421 in words is "twenty million, seven hundred thirty-one thousand, four hundred twenty-one".