261503551 has 4 divisors (see below), whose sum is σ = 262948504. Its totient is φ = 260058600.

The previous prime is 261503477. The next prime is 261503611. The reversal of 261503551 is 155305162.

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

It is a cyclic number.

It is not a de Polignac number, because 261503551 - 2¹³ = 261495359 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261503051) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 722205 + ... + 722566.

It is an arithmetic number, because the mean of its divisors is an integer number (65737126).

Almost surely, 2^261503551 is an apocalyptic number.

261503551 is a deficient number, since it is larger than the sum of its proper divisors (1444953).

261503551 is a wasteful number, since it uses less digits than its factorization.

261503551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1444952.

The product of its (nonzero) digits is 4500, while the sum is 28.

The square root of 261503551 is about 16171.0714239966. The cubic root of 261503551 is about 639.4783762423.

The spelling of 261503551 in words is "two hundred sixty-one million, five hundred three thousand, five hundred fifty-one".