261551651 has 4 divisors (see below), whose sum is σ = 261710592. Its totient is φ = 261392712.

The previous prime is 261551617. The next prime is 261551677. The reversal of 261551651 is 156155162.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-261551651 is a prime.

It is a super-2 number, since 2×261551651² = 136818532281651602, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (261551051) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 76976 + ... + 80301.

It is an arithmetic number, because the mean of its divisors is an integer number (65427648).

Almost surely, 2^261551651 is an apocalyptic number.

261551651 is a deficient number, since it is larger than the sum of its proper divisors (158941).

261551651 is a wasteful number, since it uses less digits than its factorization.

261551651 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 158940.

The product of its digits is 9000, while the sum is 32.

The square root of 261551651 is about 16172.5585792725. The cubic root of 261551651 is about 639.5175816044.

The spelling of 261551651 in words is "two hundred sixty-one million, five hundred fifty-one thousand, six hundred fifty-one".