2155681 has 4 divisors (see below), whose sum is σ = 2351664. Its totient is φ = 1959700.

The previous prime is 2155667. The next prime is 2155691. The reversal of 2155681 is 1865512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 2155681 - 2¹¹ = 2153633 is a prime.

It is a super-2 number, since 2×2155681² = 9293921147522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2155661) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 97975 + ... + 97996.

It is an arithmetic number, because the mean of its divisors is an integer number (587916).

2^2155681 is an apocalyptic number.

It is an amenable number.

2155681 is a deficient number, since it is larger than the sum of its proper divisors (195983).

2155681 is a wasteful number, since it uses less digits than its factorization.

2155681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 195982.

The product of its digits is 2400, while the sum is 28.

The square root of 2155681 is about 1468.2237567891. The cubic root of 2155681 is about 129.1798664739.

The spelling of 2155681 in words is "two million, one hundred fifty-five thousand, six hundred eighty-one".