21421031 has 4 divisors (see below), whose sum is σ = 22112064. Its totient is φ = 20730000.

The previous prime is 21420991. The next prime is 21421051. The reversal of 21421031 is 13012412.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21421031 - 2⁶ = 21420967 is a prime.

It is a super-2 number, since 2×21421031² = 917721138205922, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21420997 and 21421015.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21421051) 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, 345470 + ... + 345531.

It is an arithmetic number, because the mean of its divisors is an integer number (5528016).

Almost surely, 2^21421031 is an apocalyptic number.

21421031 is a deficient number, since it is larger than the sum of its proper divisors (691033).

21421031 is an equidigital number, since it uses as much as digits as its factorization.

21421031 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 691032.

The product of its (nonzero) digits is 48, while the sum is 14.

The square root of 21421031 is about 4628.2859678287. The cubic root of 21421031 is about 277.7240287056.

Adding to 21421031 its reverse (13012412), we get a palindrome (34433443).

The spelling of 21421031 in words is "twenty-one million, four hundred twenty-one thousand, thirty-one".