20661345 has 32 divisors (see below), whose sum is σ = 37923840. Its totient is φ = 10661760.

The previous prime is 20661323. The next prime is 20661367. The reversal of 20661345 is 54316602.

20661345 is a `hidden beast` number, since 2 + 0 + 6 + 613 + 45 = 666.

It is an interprime number because it is at equal distance from previous prime (20661323) and next prime (20661367).

It is not a de Polignac number, because 20661345 - 2¹³ = 20653153 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

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 31 ways as a sum of consecutive naturals, for example, 1717 + ... + 6653.

It is an arithmetic number, because the mean of its divisors is an integer number (1185120).

Almost surely, 2^20661345 is an apocalyptic number.

It is an amenable number.

20661345 is a deficient number, since it is larger than the sum of its proper divisors (17262495).

20661345 is a wasteful number, since it uses less digits than its factorization.

20661345 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4982 (or 4976 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 27.

The square root of 20661345 is about 4545.4752226802. The cubic root of 20661345 is about 274.4013201989.

Subtracting from 20661345 its product of nonzero digits (4320), we obtain a square (20657025 = 4545²).

Adding to 20661345 its reverse (54316602), we get a palindrome (74977947).

The spelling of 20661345 in words is "twenty million, six hundred sixty-one thousand, three hundred forty-five".