1661617501 has 2 divisors, whose sum is σ = 1661617502. Its totient is φ = 1661617500.

The previous prime is 1661617471. The next prime is 1661617511. The reversal of 1661617501 is 1057161661.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 916272900 + 745344601 = 30270^2 + 27301^2 .

It is a cyclic number.

It is not a de Polignac number, because 1661617501 - 2²¹ = 1659520349 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1661617511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 830808750 + 830808751.

It is an arithmetic number, because the mean of its divisors is an integer number (830808751).

Almost surely, 2^1661617501 is an apocalyptic number.

It is an amenable number.

1661617501 is a deficient number, since it is larger than the sum of its proper divisors (1).

1661617501 is an equidigital number, since it uses as much as digits as its factorization.

1661617501 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7560, while the sum is 34.

The square root of 1661617501 is about 40762.9427421525. The cubic root of 1661617501 is about 1184.4326008248.

The spelling of 1661617501 in words is "one billion, six hundred sixty-one million, six hundred seventeen thousand, five hundred one".