1621640 has 32 divisors (see below), whose sum is σ = 3706560. Its totient is φ = 638400.

The previous prime is 1621639. The next prime is 1621643. The reversal of 1621640 is 461261.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1621643) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2555 + ... + 3125.

It is an arithmetic number, because the mean of its divisors is an integer number (115830).

2^1621640 is an apocalyptic number.

1621640 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 1621640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1853280).

1621640 is an abundant number, since it is smaller than the sum of its proper divisors (2084920).

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

1621640 is a wasteful number, since it uses less digits than its factorization.

1621640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 653 (or 649 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 20.

The square root of 1621640 is about 1273.4362960117. The cubic root of 1621640 is about 117.4856478622.

The spelling of 1621640 in words is "one million, six hundred twenty-one thousand, six hundred forty".