646243920 has 280 divisors, whose sum is σ = 2576192256. Its totient is φ = 147619584.

The previous prime is 646243909. The next prime is 646243931. The reversal of 646243920 is 29342646.

646243920 is a `hidden beast` number, since 6 + 4 + 624 + 3 + 9 + 20 = 666.

It is an interprime number because it is at equal distance from previous prime (646243909) and next prime (646243931).

It is a tau number, because it is divible by the number of its divisors (280).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 407449 + ... + 409031.

Almost surely, 2^646243920 is an apocalyptic number.

646243920 is a gapful number since it is divisible by the number (60) 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 646243920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1288096128).

646243920 is an abundant number, since it is smaller than the sum of its proper divisors (1929948336).

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

646243920 is a wasteful number, since it uses less digits than its factorization.

646243920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1621 (or 1600 counting only the distinct ones).

The product of its (nonzero) digits is 62208, while the sum is 36.

The square root of 646243920 is about 25421.3280534279. The cubic root of 646243920 is about 864.5673357173.

The spelling of 646243920 in words is "six hundred forty-six million, two hundred forty-three thousand, nine hundred twenty".