21231015 has 16 divisors (see below), whose sum is σ = 36583008. Its totient is φ = 10452096.

The previous prime is 21230969. The next prime is 21231029. The reversal of 21231015 is 51013212.

It is not a de Polignac number, because 21231015 - 2¹⁶ = 21165479 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a junction number, because it is equal to n+sod(n) for n = 21230985 and 21231003.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 54244 + ... + 54633.

It is an arithmetic number, because the mean of its divisors is an integer number (2286438).

Almost surely, 2^21231015 is an apocalyptic number.

21231015 is a deficient number, since it is larger than the sum of its proper divisors (15351993).

21231015 is a wasteful number, since it uses less digits than its factorization.

21231015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 108898.

The product of its (nonzero) digits is 60, while the sum is 15.

The square root of 21231015 is about 4607.7125561389. The cubic root of 21231015 is about 276.9004016630.

Adding to 21231015 its reverse (51013212), we get a palindrome (72244227).

The spelling of 21231015 in words is "twenty-one million, two hundred thirty-one thousand, fifteen".