2157720 has 32 divisors (see below), whose sum is σ = 6473520. Its totient is φ = 575360.

The previous prime is 2157709. The next prime is 2157721. The reversal of 2157720 is 277512.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is an Ulam number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2157721) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8871 + ... + 9110.

2^2157720 is an apocalyptic number.

2157720 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

2157720 is an abundant number, since it is smaller than the sum of its proper divisors (4315800).

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

2157720 is a wasteful number, since it uses less digits than its factorization.

2157720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17995 (or 17991 counting only the distinct ones).

The product of its (nonzero) digits is 980, while the sum is 24.

The square root of 2157720 is about 1468.9179691188. The cubic root of 2157720 is about 129.2205828793.

The spelling of 2157720 in words is "two million, one hundred fifty-seven thousand, seven hundred twenty".