21051915 has 8 divisors (see below), whose sum is σ = 33683088. Its totient is φ = 11227680.

The previous prime is 21051913. The next prime is 21051949. The reversal of 21051915 is 51915012.

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

It is not a de Polignac number, because 21051915 - 2¹ = 21051913 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21051913) 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, 701716 + ... + 701745.

It is an arithmetic number, because the mean of its divisors is an integer number (4210386).

Almost surely, 2^21051915 is an apocalyptic number.

21051915 is a deficient number, since it is larger than the sum of its proper divisors (12631173).

21051915 is a wasteful number, since it uses less digits than its factorization.

21051915 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1403469.

The product of its (nonzero) digits is 450, while the sum is 24.

The square root of 21051915 is about 4588.2365893663. The cubic root of 21051915 is about 276.1195790389.

Adding to 21051915 its reverse (51915012), we get a palindrome (72966927).

It can be divided in two parts, 210 and 51915, that added together give a palindrome (52125).

The spelling of 21051915 in words is "twenty-one million, fifty-one thousand, nine hundred fifteen".