21705520261 has 8 divisors (see below), whose sum is σ = 22063703904. Its totient is φ = 21347412720.

The previous prime is 21705520247. The next prime is 21705520267. The reversal of 21705520261 is 16202550712.

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 21705520261 - 2⁵ = 21705520229 is a prime.

It is a super-2 number, since 2×21705520261² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21705520267) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1011930 + ... + 1033156.

It is an arithmetic number, because the mean of its divisors is an integer number (2757962988).

Almost surely, 2^21705520261 is an apocalyptic number.

It is an amenable number.

21705520261 is a deficient number, since it is larger than the sum of its proper divisors (358183643).

21705520261 is a wasteful number, since it uses less digits than its factorization.

21705520261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38051.

The product of its (nonzero) digits is 8400, while the sum is 31.

The spelling of 21705520261 in words is "twenty-one billion, seven hundred five million, five hundred twenty thousand, two hundred sixty-one".