1721988 has 36 divisors (see below), whose sum is σ = 4496128. Its totient is φ = 555120.

The previous prime is 1721983. The next prime is 1722013. The reversal of 1721988 is 8891271.

It is a tau number, because it is divible by the number of its divisors (36).

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

It is not an unprimeable number, because it can be changed into a prime (1721983) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 345 + ... + 1887.

2^1721988 is an apocalyptic number.

1721988 is a gapful number since it is divisible by the number (18) 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 1721988, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2248064).

1721988 is an abundant number, since it is smaller than the sum of its proper divisors (2774140).

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

1721988 is a wasteful number, since it uses less digits than its factorization.

1721988 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1584 (or 1579 counting only the distinct ones).

The product of its digits is 8064, while the sum is 36.

The square root of 1721988 is about 1312.2454038784. The cubic root of 1721988 is about 119.8606716260.

The spelling of 1721988 in words is "one million, seven hundred twenty-one thousand, nine hundred eighty-eight".