261621749 has 2 divisors, whose sum is σ = 261621750. Its totient is φ = 261621748.

The previous prime is 261621743. The next prime is 261621793. The reversal of 261621749 is 947126162.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 219928900 + 41692849 = 14830^2 + 6457^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261621749 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (261621743) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 130810874 + 130810875.

It is an arithmetic number, because the mean of its divisors is an integer number (130810875).

Almost surely, 2^261621749 is an apocalyptic number.

It is an amenable number.

261621749 is a deficient number, since it is larger than the sum of its proper divisors (1).

261621749 is an equidigital number, since it uses as much as digits as its factorization.

261621749 is an evil number, because the sum of its binary digits is even.

The product of its digits is 36288, while the sum is 38.

The square root of 261621749 is about 16174.7256236389. The cubic root of 261621749 is about 639.5747084969.

The spelling of 261621749 in words is "two hundred sixty-one million, six hundred twenty-one thousand, seven hundred forty-nine".