1621655640 has 384 divisors, whose sum is σ = 6179846400. Its totient is φ = 378846720.

The previous prime is 1621655639. The next prime is 1621655677. The reversal of 1621655640 is 465561261.

1621655640 is a `hidden beast` number, since 1 + 6 + 2 + 1 + 6 + 5 + 5 + 640 = 666.

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

It is a junction number, because it is equal to n+sod(n) for n = 1621655595 and 1621655604.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 3100419 + ... + 3100941.

It is an arithmetic number, because the mean of its divisors is an integer number (16093350).

Almost surely, 2^1621655640 is an apocalyptic number.

1621655640 is a gapful number since it is divisible by the number (10) 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 1621655640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3089923200).

1621655640 is an abundant number, since it is smaller than the sum of its proper divisors (4558190760).

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

1621655640 is a wasteful number, since it uses less digits than its factorization.

1621655640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 589 (or 573 counting only the distinct ones).

The product of its (nonzero) digits is 43200, while the sum is 36.

The square root of 1621655640 is about 40269.7856959781. The cubic root of 1621655640 is about 1174.8602556004.

The spelling of 1621655640 in words is "one billion, six hundred twenty-one million, six hundred fifty-five thousand, six hundred forty".