261621439 has 4 divisors (see below), whose sum is σ = 265306320. Its totient is φ = 257936560.

The previous prime is 261621433. The next prime is 261621461. The reversal of 261621439 is 934126162.

It is a happy number.

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-261621439 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 (261621433) 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, 1842334 + ... + 1842475.

It is an arithmetic number, because the mean of its divisors is an integer number (66326580).

Almost surely, 2^261621439 is an apocalyptic number.

261621439 is a deficient number, since it is larger than the sum of its proper divisors (3684881).

261621439 is an equidigital number, since it uses as much as digits as its factorization.

261621439 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3684880.

The product of its digits is 15552, while the sum is 34.

The square root of 261621439 is about 16174.7160407841. The cubic root of 261621439 is about 639.5744558826.

The spelling of 261621439 in words is "two hundred sixty-one million, six hundred twenty-one thousand, four hundred thirty-nine".