21505707 has 6 divisors (see below), whose sum is σ = 31063812. Its totient is φ = 14337132.

The previous prime is 21505699. The next prime is 21505709. The reversal of 21505707 is 70750512.

It is not a de Polignac number, because 21505707 - 2³ = 21505699 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21505709) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1194753 + ... + 1194770.

It is an arithmetic number, because the mean of its divisors is an integer number (5177302).

Almost surely, 2^21505707 is an apocalyptic number.

21505707 is a deficient number, since it is larger than the sum of its proper divisors (9558105).

21505707 is a wasteful number, since it uses less digits than its factorization.

21505707 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2389529 (or 2389526 counting only the distinct ones).

The product of its (nonzero) digits is 2450, while the sum is 27.

The square root of 21505707 is about 4637.4246085516. The cubic root of 21505707 is about 278.0894895032.

The spelling of 21505707 in words is "twenty-one million, five hundred five thousand, seven hundred seven".