21503705 has 8 divisors (see below), whose sum is σ = 25948104. Its totient is φ = 17107200.

The previous prime is 21503693. The next prime is 21503719. The reversal of 21503705 is 50730512.

It can be written as a sum of positive squares in 4 ways, for example, as 1936 + 21501769 = 44^2 + 4637^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21503705 - 2¹⁰ = 21502681 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10976 + ... + 12785.

It is an arithmetic number, because the mean of its divisors is an integer number (3243513).

Almost surely, 2^21503705 is an apocalyptic number.

It is an amenable number.

21503705 is a deficient number, since it is larger than the sum of its proper divisors (4444399).

21503705 is a wasteful number, since it uses less digits than its factorization.

21503705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 23947.

The product of its (nonzero) digits is 1050, while the sum is 23.

The square root of 21503705 is about 4637.2087509622. The cubic root of 21503705 is about 278.0808599732.

The spelling of 21503705 in words is "twenty-one million, five hundred three thousand, seven hundred five".