21231021 has 8 divisors (see below), whose sum is σ = 32352064. Its totient is φ = 12132000.

The previous prime is 21230969. The next prime is 21231029. The reversal of 21231021 is 12013212.

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

It is not a de Polignac number, because 21231021 - 2⁹ = 21230509 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21230988 and 21231006.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21231029) 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, 505480 + ... + 505521.

It is an arithmetic number, because the mean of its divisors is an integer number (4044008).

Almost surely, 2^21231021 is an apocalyptic number.

21231021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21231021 is a deficient number, since it is larger than the sum of its proper divisors (11121043).

21231021 is a wasteful number, since it uses less digits than its factorization.

21231021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1011011.

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

The square root of 21231021 is about 4607.7132072211. The cubic root of 21231021 is about 276.9004277476.

Adding to 21231021 its reverse (12013212), we get a palindrome (33244233).

The spelling of 21231021 in words is "twenty-one million, two hundred thirty-one thousand, twenty-one".