20561670 has 96 divisors (see below), whose sum is σ = 57620160. Its totient is φ = 5068800.

The previous prime is 20561663. The next prime is 20561683. The reversal of 20561670 is 7616502.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 136095 + ... + 136245.

It is an arithmetic number, because the mean of its divisors is an integer number (600210).

Almost surely, 2^20561670 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20561670, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28810080).

20561670 is an abundant number, since it is smaller than the sum of its proper divisors (37058490).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20561670 is a wasteful number, since it uses less digits than its factorization.

20561670 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 270 (or 267 counting only the distinct ones).

The product of its (nonzero) digits is 2520, while the sum is 27.

The square root of 20561670 is about 4534.4977671182. The cubic root of 20561670 is about 273.9593507105.

The spelling of 20561670 in words is "twenty million, five hundred sixty-one thousand, six hundred seventy".