26251561 has 4 divisors (see below), whose sum is σ = 30001792. Its totient is φ = 22501332.

The previous prime is 26251549. The next prime is 26251571. The reversal of 26251561 is 16515262.

26251561 = 770² + 771² + ... + 811².

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 26251561 - 2¹⁵ = 26218793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (26251531) 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, 1875105 + ... + 1875118.

It is an arithmetic number, because the mean of its divisors is an integer number (7500448).

Almost surely, 2^26251561 is an apocalyptic number.

It is an amenable number.

26251561 is a deficient number, since it is larger than the sum of its proper divisors (3750231).

26251561 is an equidigital number, since it uses as much as digits as its factorization.

26251561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3750230.

The product of its digits is 3600, while the sum is 28.

The square root of 26251561 is about 5123.6277187165. The cubic root of 26251561 is about 297.2019886085.

It can be divided in two parts, 2625 and 1561, that added together give a triangular number (4186 = T₉₁).

The spelling of 26251561 in words is "twenty-six million, two hundred fifty-one thousand, five hundred sixty-one".