21001715 has 32 divisors (see below), whose sum is σ = 31186944. Its totient is φ = 13248000.

The previous prime is 21001711. The next prime is 21001763. The reversal of 21001715 is 51710012.

It is not a de Polignac number, because 21001715 - 2² = 21001711 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (17).

It is a junction number, because it is equal to n+sod(n) for n = 21001693 and 21001702.

It is not an unprimeable number, because it can be changed into a prime (21001711) 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 31 ways as a sum of consecutive naturals, for example, 27590 + ... + 28340.

It is an arithmetic number, because the mean of its divisors is an integer number (974592).

Almost surely, 2^21001715 is an apocalyptic number.

21001715 is a deficient number, since it is larger than the sum of its proper divisors (10185229).

21001715 is a wasteful number, since it uses less digits than its factorization.

21001715 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 827.

The product of its (nonzero) digits is 70, while the sum is 17.

The square root of 21001715 is about 4582.7628129765. The cubic root of 21001715 is about 275.8999278384.

Adding to 21001715 its reverse (51710012), we get a palindrome (72711727).

The spelling of 21001715 in words is "twenty-one million, one thousand, seven hundred fifteen".