21351015 has 72 divisors (see below), whose sum is σ = 45029088. Its totient is φ = 9313920.

The previous prime is 21351013. The next prime is 21351017. The reversal of 21351015 is 51015312.

It is an interprime number because it is at equal distance from previous prime (21351013) and next prime (21351017).

It is not a de Polignac number, because 21351015 - 2¹ = 21351013 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21351013) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 50505 + ... + 50925.

It is an arithmetic number, because the mean of its divisors is an integer number (625404).

Almost surely, 2^21351015 is an apocalyptic number.

21351015 is an abundant number, since it is smaller than the sum of its proper divisors (23678073).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21351015 is a wasteful number, since it uses less digits than its factorization.

21351015 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 469 (or 459 counting only the distinct ones).

The product of its (nonzero) digits is 150, while the sum is 18.

The square root of 21351015 is about 4620.7158536313. The cubic root of 21351015 is about 277.4211122240.

Adding to 21351015 its reverse (51015312), we get a palindrome (72366327).

The spelling of 21351015 in words is "twenty-one million, three hundred fifty-one thousand, fifteen".