21020715 has 56 divisors (see below), whose sum is σ = 38823360. Its totient is φ = 10917504.

The previous prime is 21020683. The next prime is 21020719. The reversal of 21020715 is 51702012.

It is not a de Polignac number, because 21020715 - 2⁵ = 21020683 is a prime.

It is a super-2 number, since 2×21020715² = 883740918222450, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21020719) by changing a digit.

It is a polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 266046 + ... + 266124.

Almost surely, 2^21020715 is an apocalyptic number.

21020715 is a deficient number, since it is larger than the sum of its proper divisors (17802645).

21020715 is an frugal number, since it uses more digits than its factorization.

21020715 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 175 (or 160 counting only the distinct ones).

The product of its (nonzero) digits is 140, while the sum is 18.

The square root of 21020715 is about 4584.8353296493. The cubic root of 21020715 is about 275.9831038806.

Adding to 21020715 its reverse (51702012), we get a palindrome (72722727).

The spelling of 21020715 in words is "twenty-one million, twenty thousand, seven hundred fifteen".