21231013 has 4 divisors (see below), whose sum is σ = 21499840. Its totient is φ = 20962188.

The previous prime is 21230969. The next prime is 21231029. The reversal of 21231013 is 31013212.

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 a de Polignac number, because none of the positive numbers 2^k-21231013 is a prime.

It is a Duffinian number.

It is a zygodrome in base 4.

It is a junction number, because it is equal to n+sod(n) for n = 21230984 and 21231002.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21231313) 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, 134295 + ... + 134452.

It is an arithmetic number, because the mean of its divisors is an integer number (5374960).

Almost surely, 2^21231013 is an apocalyptic number.

It is an amenable number.

21231013 is a deficient number, since it is larger than the sum of its proper divisors (268827).

21231013 is an equidigital number, since it uses as much as digits as its factorization.

21231013 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 268826.

The product of its (nonzero) digits is 36, while the sum is 13.

The square root of 21231013 is about 4607.7123391115. The cubic root of 21231013 is about 276.9003929682.

Adding to 21231013 its reverse (31013212), we get a palindrome (52244225).

It can be divided in two parts, 2123 and 1013, that added together give a square (3136 = 56²).

The spelling of 21231013 in words is "twenty-one million, two hundred thirty-one thousand, thirteen".