2155651621 has 2 divisors, whose sum is σ = 2155651622. Its totient is φ = 2155651620.

The previous prime is 2155651607. The next prime is 2155651651. The reversal of 2155651621 is 1261565512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1908816100 + 246835521 = 43690^2 + 15711^2 .

It is a cyclic number.

It is not a de Polignac number, because 2155651621 - 2⁹ = 2155651109 is a prime.

It is a super-2 number, since 2×2155651621² = 9293667822239855282, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2155651601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1077825810 + 1077825811.

It is an arithmetic number, because the mean of its divisors is an integer number (1077825811).

Almost surely, 2^2155651621 is an apocalyptic number.

It is an amenable number.

2155651621 is a deficient number, since it is larger than the sum of its proper divisors (1).

2155651621 is an equidigital number, since it uses as much as digits as its factorization.

2155651621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18000, while the sum is 34.

The square root of 2155651621 is about 46428.9954769646. The cubic root of 2155651621 is about 1291.7927962262.

The spelling of 2155651621 in words is "two billion, one hundred fifty-five million, six hundred fifty-one thousand, six hundred twenty-one".