15978420 has 72 divisors (see below), whose sum is σ = 50155560. Its totient is φ = 4112640.

The previous prime is 15978383. The next prime is 15978421. The reversal of 15978420 is 2487951.

It can be written as a sum of positive squares in 4 ways, for example, as 5363856 + 10614564 = 2316^2 + 3258^2 .

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (15978421) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3690 + ... + 6750.

It is an arithmetic number, because the mean of its divisors is an integer number (696605).

Almost surely, 2^15978420 is an apocalyptic number.

15978420 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 15978420, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25077780).

15978420 is an abundant number, since it is smaller than the sum of its proper divisors (34177140).

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

15978420 is a wasteful number, since it uses less digits than its factorization.

15978420 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3105 (or 3100 counting only the distinct ones).

The product of its (nonzero) digits is 20160, while the sum is 36.

The square root of 15978420 is about 3997.3015898228. The cubic root of 15978420 is about 251.8708711074.

The spelling of 15978420 in words is "fifteen million, nine hundred seventy-eight thousand, four hundred twenty".