1651501661 has 4 divisors (see below), whose sum is σ = 1656491424. Its totient is φ = 1646511900.

The previous prime is 1651501609. The next prime is 1651501699. The reversal of 1651501661 is 1661051561.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 1661051561 = 13 ⋅127773197.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1651501661 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1651561661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2494385 + ... + 2495046.

It is an arithmetic number, because the mean of its divisors is an integer number (414122856).

Almost surely, 2^1651501661 is an apocalyptic number.

It is an amenable number.

1651501661 is a deficient number, since it is larger than the sum of its proper divisors (4989763).

1651501661 is an equidigital number, since it uses as much as digits as its factorization.

1651501661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4989762.

The product of its (nonzero) digits is 5400, while the sum is 32.

The square root of 1651501661 is about 40638.6719886366. The cubic root of 1651501661 is about 1182.0241188177.

The spelling of 1651501661 in words is "one billion, six hundred fifty-one million, five hundred one thousand, six hundred sixty-one".