2190645721 has 24 divisors (see below), whose sum is σ = 2620650240. Its totient is φ = 1813804800.

The previous prime is 2190645719. The next prime is 2190645731. The reversal of 2190645721 is 1275460912.

It is not a de Polignac number, because 2190645721 - 2¹ = 2190645719 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2190645731) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 87435 + ... + 109663.

It is an arithmetic number, because the mean of its divisors is an integer number (109193760).

Almost surely, 2^2190645721 is an apocalyptic number.

It is an amenable number.

2190645721 is a deficient number, since it is larger than the sum of its proper divisors (430004519).

2190645721 is a wasteful number, since it uses less digits than its factorization.

2190645721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22305 (or 22288 counting only the distinct ones).

The product of its (nonzero) digits is 30240, while the sum is 37.

The square root of 2190645721 is about 46804.3344253500. The cubic root of 2190645721 is about 1298.7454802914.

It can be divided in two parts, 219064 and 5721, that added together give a triangular number (224785 = T₆₇₀).

The spelling of 2190645721 in words is "two billion, one hundred ninety million, six hundred forty-five thousand, seven hundred twenty-one".