1545645721 has 2 divisors, whose sum is σ = 1545645722. Its totient is φ = 1545645720.

The previous prime is 1545645679. The next prime is 1545645727. The reversal of 1545645721 is 1275465451.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1007173696 + 538472025 = 31736^2 + 23205^2 .

It is a cyclic number.

It is not a de Polignac number, because 1545645721 - 2²¹ = 1543548569 is a prime.

It is not a weakly prime, because it can be changed into another prime (1545645727) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 772822860 + 772822861.

It is an arithmetic number, because the mean of its divisors is an integer number (772822861).

Almost surely, 2^1545645721 is an apocalyptic number.

It is an amenable number.

1545645721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1545645721 is an equidigital number, since it uses as much as digits as its factorization.

1545645721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 168000, while the sum is 40.

The square root of 1545645721 is about 39314.7010798760. The cubic root of 1545645721 is about 1156.2098155754.

The spelling of 1545645721 in words is "one billion, five hundred forty-five million, six hundred forty-five thousand, seven hundred twenty-one".