21312021 has 8 divisors (see below), whose sum is σ = 28457440. Its totient is φ = 14187312.

The previous prime is 21312019. The next prime is 21312023. The reversal of 21312021 is 12021312.

It is an interprime number because it is at equal distance from previous prime (21312019) and next prime (21312023).

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

It is not a de Polignac number, because 21312021 - 2¹ = 21312019 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21311988 and 21312006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21312023) 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, 2590 + ... + 7023.

It is an arithmetic number, because the mean of its divisors is an integer number (3557180).

Almost surely, 2^21312021 is an apocalyptic number.

It is an amenable number.

21312021 is a deficient number, since it is larger than the sum of its proper divisors (7145419).

21312021 is an equidigital number, since it uses as much as digits as its factorization.

21312021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10355.

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 21312021 is about 4616.4944492548. The cubic root of 21312021 is about 277.2521218015.

Adding to 21312021 its reverse (12021312), we get a palindrome (33333333).

The spelling of 21312021 in words is "twenty-one million, three hundred twelve thousand, twenty-one".