21015121 has 8 divisors (see below), whose sum is σ = 22330080. Its totient is φ = 19721088.

The previous prime is 21015119. The next prime is 21015139. The reversal of 21015121 is 12151012.

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

It is not a de Polignac number, because 21015121 - 2¹ = 21015119 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21015161) 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, 3136 + ... + 7201.

It is an arithmetic number, because the mean of its divisors is an integer number (2791260).

Almost surely, 2^21015121 is an apocalyptic number.

It is an amenable number.

21015121 is a deficient number, since it is larger than the sum of its proper divisors (1314959).

21015121 is a wasteful number, since it uses less digits than its factorization.

21015121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10463.

The product of its (nonzero) digits is 20, while the sum is 13.

The square root of 21015121 is about 4584.2252344317. The cubic root of 21015121 is about 275.9586203104.

Adding to 21015121 its reverse (12151012), we get a palindrome (33166133).

The spelling of 21015121 in words is "twenty-one million, fifteen thousand, one hundred twenty-one".