19661940 has 120 divisors (see below), whose sum is σ = 63118440. Its totient is φ = 5121792.

The previous prime is 19661923. The next prime is 19661951. The reversal of 19661940 is 4916691.

It can be written as a sum of positive squares in 4 ways, for example, as 8088336 + 11573604 = 2844^2 + 3402^2 .

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 = 19661895 and 19661904.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 85746 + ... + 85974.

It is an arithmetic number, because the mean of its divisors is an integer number (525987).

Almost surely, 2^19661940 is an apocalyptic number.

19661940 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 19661940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31559220).

19661940 is an abundant number, since it is smaller than the sum of its proper divisors (43456500).

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

19661940 is a wasteful number, since it uses less digits than its factorization.

19661940 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 303 (or 292 counting only the distinct ones).

The product of its (nonzero) digits is 11664, while the sum is 36.

The square root of 19661940 is about 4434.1786161588. The cubic root of 19661940 is about 269.9036693389.

The spelling of 19661940 in words is "nineteen million, six hundred sixty-one thousand, nine hundred forty".