20100421 has 4 divisors (see below), whose sum is σ = 21927744. Its totient is φ = 18273100.

The previous prime is 20100419. The next prime is 20100433. The reversal of 20100421 is 12400102.

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.

It is a cyclic number.

It is not a de Polignac number, because 20100421 - 2¹ = 20100419 is a prime.

It is a super-3 number, since 3×20100421³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20100398 and 20100407.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20100401) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 913645 + ... + 913666.

It is an arithmetic number, because the mean of its divisors is an integer number (5481936).

Almost surely, 2^20100421 is an apocalyptic number.

It is an amenable number.

20100421 is a deficient number, since it is larger than the sum of its proper divisors (1827323).

20100421 is a wasteful number, since it uses less digits than its factorization.

20100421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1827322.

The product of its (nonzero) digits is 16, while the sum is 10.

The square root of 20100421 is about 4483.3493060434. The cubic root of 20100421 is about 271.8953109589.

Adding to 20100421 its reverse (12400102), we get a palindrome (32500523).

The spelling of 20100421 in words is "twenty million, one hundred thousand, four hundred twenty-one".