100661561 has 32 divisors (see below), whose sum is σ = 136055808. Its totient is φ = 71922240.

The previous prime is 100661551. The next prime is 100661567. The reversal of 100661561 is 165166001.

It is not a de Polignac number, because 100661561 - 2¹⁴ = 100645177 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 100661561.

It is not an unprimeable number, because it can be changed into a prime (100661567) 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, 227006 + ... + 227448.

It is an arithmetic number, because the mean of its divisors is an integer number (4251744).

Almost surely, 2^100661561 is an apocalyptic number.

100661561 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

100661561 is a deficient number, since it is larger than the sum of its proper divisors (35394247).

100661561 is a wasteful number, since it uses less digits than its factorization.

100661561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 701.

The product of its (nonzero) digits is 1080, while the sum is 26.

The square root of 100661561 is about 10033.0235223486. The cubic root of 100661561 is about 465.1801991692.

The spelling of 100661561 in words is "one hundred million, six hundred sixty-one thousand, five hundred sixty-one".