2154844907721 has 27 divisors (see below), whose sum is σ = 3421313685517. Its totient is φ = 1305937251960.

The previous prime is 2154844907687. The next prime is 2154844907737. The reversal of 2154844907721 is 1277094484512.

It is a happy number.

The square root of 2154844907721 is 1467939.

It is a perfect power (a square), and thus also a powerful number.

2154844907721 is a `hidden beast` number, since 2 + 1 + 5 + 4 + 84 + 490 + 7 + 72 + 1 = 666.

It is not a de Polignac number, because 2154844907721 - 2¹¹ = 2154844905673 is a prime.

It is a super-2 number, since 2×2154844907721² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2154844907771) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 48419746 + ... + 48464228.

Almost surely, 2^{2154844907721} is an apocalyptic number.

2154844907721 is the 1467939-th square number.

2154844907721 is the 733970-th centered octagonal number.

It is an amenable number.

2154844907721 is a deficient number, since it is larger than the sum of its proper divisors (1266468777796).

2154844907721 is an frugal number, since it uses more digits than its factorization.

2154844907721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 88994 (or 44497 counting only the distinct ones).

The product of its (nonzero) digits is 4515840, while the sum is 54.

The spelling of 2154844907721 in words is "two trillion, one hundred fifty-four billion, eight hundred forty-four million, nine hundred seven thousand, seven hundred twenty-one".