20400660 has 180 divisors, whose sum is σ = 74735892. Its totient is φ = 4644864.

The previous prime is 20400637. The next prime is 20400671. The reversal of 20400660 is 6600402.

20400660 is a `hidden beast` number, since 2 + 0 + 4 + 0 + 0 + 660 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 15256836 + 5143824 = 3906^2 + 2268^2 .

It is a tau number, because it is divible by the number of its divisors (180).

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a congruent 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 59 ways as a sum of consecutive naturals, for example, 79252 + ... + 79508.

Almost surely, 2^20400660 is an apocalyptic number.

20400660 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20400660, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37367946).

20400660 is an abundant number, since it is smaller than the sum of its proper divisors (54335232).

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

20400660 is a wasteful number, since it uses less digits than its factorization.

20400660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 292 (or 274 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 20400660 is about 4516.7089788916. The cubic root of 20400660 is about 273.2423882775.

The spelling of 20400660 in words is "twenty million, four hundred thousand, six hundred sixty".