1651382721 has 10 divisors (see below), whose sum is σ = 2466880482. Its totient is φ = 1100921760.

The previous prime is 1651382657. The next prime is 1651382749. The reversal of 1651382721 is 1272831561.

It can be written as a sum of positive squares in only one way, i.e., 1643897025 + 7485696 = 40545^2 + 2736^2 .

It is not a de Polignac number, because 1651382721 - 2⁶ = 1651382657 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1651382921) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 10193640 + ... + 10193801.

Almost surely, 2^1651382721 is an apocalyptic number.

It is an amenable number.

1651382721 is a deficient number, since it is larger than the sum of its proper divisors (815497761).

1651382721 is an equidigital number, since it uses as much as digits as its factorization.

1651382721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20387453 (or 20387444 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 1651382721 is about 40637.2085778539. The cubic root of 1651382721 is about 1181.9957419517.

The spelling of 1651382721 in words is "one billion, six hundred fifty-one million, three hundred eighty-two thousand, seven hundred twenty-one".