261553772421021 has 32 divisors (see below), whose sum is σ = 368063710986240. Its totient is φ = 164755071278784.

The previous prime is 261553772420911. The next prime is 261553772421047. The reversal of 261553772421021 is 120124277355162.

It is not a de Polignac number, because 261553772421021 - 2²⁶ = 261553705312157 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (261553772421421) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 715808656 + ... + 716173958.

It is an arithmetic number, because the mean of its divisors is an integer number (11501990968320).

Almost surely, 2^{261553772421021} is an apocalyptic number.

It is an amenable number.

261553772421021 is a deficient number, since it is larger than the sum of its proper divisors (106509938565219).

261553772421021 is a wasteful number, since it uses less digits than its factorization.

261553772421021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 398505.

The product of its (nonzero) digits is 1411200, while the sum is 48.

The spelling of 261553772421021 in words is "two hundred sixty-one trillion, five hundred fifty-three billion, seven hundred seventy-two million, four hundred twenty-one thousand, twenty-one".