20818421 has 8 divisors (see below), whose sum is σ = 23738904. Its totient is φ = 18086400.

The previous prime is 20818409. The next prime is 20818459. The reversal of 20818421 is 12481802.

It can be written as a sum of positive squares in 4 ways, for example, as 5522500 + 15295921 = 2350^2 + 3911^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20818421 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20818481) 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, 46880 + ... + 47321.

It is an arithmetic number, because the mean of its divisors is an integer number (2967363).

Almost surely, 2^20818421 is an apocalyptic number.

It is an amenable number.

20818421 is a deficient number, since it is larger than the sum of its proper divisors (2920483).

20818421 is a wasteful number, since it uses less digits than its factorization.

20818421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 94231.

The product of its (nonzero) digits is 1024, while the sum is 26.

The square root of 20818421 is about 4562.7207891783. The cubic root of 20818421 is about 275.0949358174.

The spelling of 20818421 in words is "twenty million, eight hundred eighteen thousand, four hundred twenty-one".