20661570 has 48 divisors (see below), whose sum is σ = 54275832. Its totient is φ = 5452800.

The previous prime is 20661551. The next prime is 20661583. The reversal of 20661570 is 7516602.

It can be written as a sum of positive squares in 4 ways, for example, as 20602521 + 59049 = 4539^2 + 243^2 .

It is a super-3 number, since 3×20661570³ (a number of 23 digits) contains 333 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 7954 + ... + 10226.

Almost surely, 2^20661570 is an apocalyptic number.

It is a pronic number, being equal to 4545×4546.

It is a practical number, because each smaller number is the sum of distinct divisors of 20661570, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27137916).

20661570 is an abundant number, since it is smaller than the sum of its proper divisors (33614262).

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

20661570 is a wasteful number, since it uses less digits than its factorization.

20661570 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2387 (or 2384 counting only the distinct ones).

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

The square root of 20661570 is about 4545.4999725003. The cubic root of 20661570 is about 274.4023162631.

It can be divided in two parts, 206 and 61570, that added together give a triangular number (61776 = T₃₅₁).

The spelling of 20661570 in words is "twenty million, six hundred sixty-one thousand, five hundred seventy".