21071505 has 64 divisors (see below), whose sum is σ = 42577920. Its totient is φ = 8660736.

The previous prime is 21071503. The next prime is 21071509. The reversal of 21071505 is 50517012.

It is not a de Polignac number, because 21071505 - 2¹ = 21071503 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is not an unprimeable number, because it can be changed into a prime (21071503) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 58516 + ... + 58874.

It is an arithmetic number, because the mean of its divisors is an integer number (665280).

Almost surely, 2^21071505 is an apocalyptic number.

It is an amenable number.

21071505 is an abundant number, since it is smaller than the sum of its proper divisors (21506415).

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

21071505 is a wasteful number, since it uses less digits than its factorization.

21071505 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 430.

The product of its (nonzero) digits is 350, while the sum is 21.

The square root of 21071505 is about 4590.3709000472. The cubic root of 21071505 is about 276.2052007914.

Adding to 21071505 its reverse (50517012), we get a palindrome (71588517).

The spelling of 21071505 in words is "twenty-one million, seventy-one thousand, five hundred five".