1661722901 has 2 divisors, whose sum is σ = 1661722902. Its totient is φ = 1661722900.

The previous prime is 1661722889. The next prime is 1661722913. The reversal of 1661722901 is 1092271661.

It is a balanced prime because it is at equal distance from previous prime (1661722889) and next prime (1661722913).

It can be written as a sum of positive squares in only one way, i.e., 961062001 + 700660900 = 31001^2 + 26470^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661722901 - 2¹⁴ = 1661706517 is a prime.

It is a super-2 number, since 2×1661722901² = 5522645999415711602, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1661722921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830861450 + 830861451.

It is an arithmetic number, because the mean of its divisors is an integer number (830861451).

Almost surely, 2^1661722901 is an apocalyptic number.

It is an amenable number.

1661722901 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661722901 is an equidigital number, since it uses as much as digits as its factorization.

1661722901 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9072, while the sum is 35.

The square root of 1661722901 is about 40764.2355625615. The cubic root of 1661722901 is about 1184.4576440044.

The spelling of 1661722901 in words is "one billion, six hundred sixty-one million, seven hundred twenty-two thousand, nine hundred one".