20521705 has 8 divisors (see below), whose sum is σ = 25475400. Its totient is φ = 15851136.

The previous prime is 20521679. The next prime is 20521723. The reversal of 20521705 is 50712502.

20521705 = 108² + 109² + ... + 397².

It can be written as a sum of positive squares in 4 ways, for example, as 127449 + 20394256 = 357^2 + 4516^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 20521705 - 2⁵ = 20521673 is a prime.

It is a super-2 number, since 2×20521705² = 842280752214050, which contains 22 as substring.

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, 70620 + ... + 70909.

It is an arithmetic number, because the mean of its divisors is an integer number (3184425).

Almost surely, 2^20521705 is an apocalyptic number.

It is an amenable number.

20521705 is a deficient number, since it is larger than the sum of its proper divisors (4953695).

20521705 is a wasteful number, since it uses less digits than its factorization.

20521705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141563.

The product of its (nonzero) digits is 700, while the sum is 22.

The square root of 20521705 is about 4530.0888512258. The cubic root of 20521705 is about 273.7817405146.

The spelling of 20521705 in words is "twenty million, five hundred twenty-one thousand, seven hundred five".