15642640 has 80 divisors (see below), whose sum is σ = 39841200. Its totient is φ = 5710848.

The previous prime is 15642637. The next prime is 15642647. The reversal of 15642640 is 4624651.

It can be written as a sum of positive squares in 8 ways, for example, as 13749264 + 1893376 = 3708^2 + 1376^2 .

It is a tau number, because it is divible by the number of its divisors (80).

It is a hoax number, since the sum of its digits (28) coincides with the sum of the digits of its distinct prime factors.

It is a junction number, because it is equal to n+sod(n) for n = 15642599 and 15642608.

It is not an unprimeable number, because it can be changed into a prime (15642647) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 175716 + ... + 175804.

It is an arithmetic number, because the mean of its divisors is an integer number (498015).

Almost surely, 2^15642640 is an apocalyptic number.

15642640 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 15642640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (19920600).

15642640 is an abundant number, since it is smaller than the sum of its proper divisors (24198560).

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

15642640 is an equidigital number, since it uses as much as digits as its factorization.

15642640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141 (or 109 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 28.

The square root of 15642640 is about 3955.0777489197. The cubic root of 15642640 is about 250.0940446180.

The spelling of 15642640 in words is "fifteen million, six hundred forty-two thousand, six hundred forty".