19721340 has 96 divisors (see below), whose sum is σ = 62496000. Its totient is φ = 5161536.

The previous prime is 19721293. The next prime is 19721371. The reversal of 19721340 is 4312791.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 31551 + ... + 32169.

It is an arithmetic number, because the mean of its divisors is an integer number (651000).

Almost surely, 2^19721340 is an apocalyptic number.

19721340 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 19721340, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31248000).

19721340 is an abundant number, since it is smaller than the sum of its proper divisors (42774660).

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

19721340 is a wasteful number, since it uses less digits than its factorization.

19721340 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 696 (or 688 counting only the distinct ones).

The product of its (nonzero) digits is 1512, while the sum is 27.

The square root of 19721340 is about 4440.8715360839. The cubic root of 19721340 is about 270.1751949386.

The spelling of 19721340 in words is "nineteen million, seven hundred twenty-one thousand, three hundred forty".