21510705 has 16 divisors (see below), whose sum is σ = 34648704. Its totient is φ = 11395200.

The previous prime is 21510703. The next prime is 21510719. The reversal of 21510705 is 50701512.

It is not a de Polignac number, because 21510705 - 2¹ = 21510703 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21510703) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2484 + ... + 7013.

It is an arithmetic number, because the mean of its divisors is an integer number (2165544).

Almost surely, 2^21510705 is an apocalyptic number.

It is an amenable number.

21510705 is a deficient number, since it is larger than the sum of its proper divisors (13137999).

21510705 is a wasteful number, since it uses less digits than its factorization.

21510705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9656.

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

The square root of 21510705 is about 4637.9634539310. The cubic root of 21510705 is about 278.1110308180. Note that the first 3 decimals are identical.

The spelling of 21510705 in words is "twenty-one million, five hundred ten thousand, seven hundred five".