21701561 has 12 divisors (see below), whose sum is σ = 25376400. Its totient is φ = 18504360.

The previous prime is 21701551. The next prime is 21701609. The reversal of 21701561 is 16510712.

It is not a de Polignac number, because 21701561 - 2⁶ = 21701497 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21701531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9290 + ... + 11388.

It is an arithmetic number, because the mean of its divisors is an integer number (2114700).

Almost surely, 2^21701561 is an apocalyptic number.

It is an amenable number.

21701561 is a deficient number, since it is larger than the sum of its proper divisors (3674839).

21701561 is a wasteful number, since it uses less digits than its factorization.

21701561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2324 (or 2317 counting only the distinct ones).

The product of its (nonzero) digits is 420, while the sum is 23.

The square root of 21701561 is about 4658.4934259909. The cubic root of 21701561 is about 278.9311332535.

The spelling of 21701561 in words is "twenty-one million, seven hundred one thousand, five hundred sixty-one".