1661457215525 has 6 divisors (see below), whose sum is σ = 2060206947282. Its totient is φ = 1329165772400.

The previous prime is 1661457215401. The next prime is 1661457215549. The reversal of 1661457215525 is 5255127541661.

It can be written as a sum of positive squares in 3 ways, for example, as 43516463236 + 1617940752289 = 208606^2 + 1271983^2 .

It is not a de Polignac number, because 1661457215525 - 2¹⁸ = 1661456953381 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 33229144286 + ... + 33229144335.

It is an arithmetic number, because the mean of its divisors is an integer number (343367824547).

Almost surely, 2^{1661457215525} is an apocalyptic number.

It is an amenable number.

1661457215525 is a deficient number, since it is larger than the sum of its proper divisors (398749731757).

1661457215525 is an equidigital number, since it uses as much as digits as its factorization.

1661457215525 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 66458288631 (or 66458288626 counting only the distinct ones).

The product of its digits is 2520000, while the sum is 50.

The spelling of 1661457215525 in words is "one trillion, six hundred sixty-one billion, four hundred fifty-seven million, two hundred fifteen thousand, five hundred twenty-five".