21154561531465 has 32 divisors (see below), whose sum is σ = 25894540891296. Its totient is φ = 16585026232320.

The previous prime is 21154561531451. The next prime is 21154561531507. The reversal of 21154561531465 is 56413516545112.

It can be written as a sum of positive squares in 16 ways, for example, as 2746934982544 + 18407626548921 = 1657388^2 + 4290411^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21154561531465 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 842094105 + ... + 842119225.

It is an arithmetic number, because the mean of its divisors is an integer number (809204402853).

Almost surely, 2^{21154561531465} is an apocalyptic number.

It is an amenable number.

21154561531465 is a deficient number, since it is larger than the sum of its proper divisors (4739979359831).

21154561531465 is a wasteful number, since it uses less digits than its factorization.

21154561531465 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28749.

The product of its digits is 2160000, while the sum is 49.

The spelling of 21154561531465 in words is "twenty-one trillion, one hundred fifty-four billion, five hundred sixty-one million, five hundred thirty-one thousand, four hundred sixty-five".