18661951 has 16 divisors (see below), whose sum is σ = 23470848. Its totient is φ = 14534520.

The previous prime is 18661943. The next prime is 18661963. The reversal of 18661951 is 15916681.

18661951 = T₂₀ + T₂₁ + ... + T₄₈₁.

It is not a de Polignac number, because 18661951 - 2³ = 18661943 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18661951.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18661991) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8316 + ... + 10318.

It is an arithmetic number, because the mean of its divisors is an integer number (1466928).

Almost surely, 2^18661951 is an apocalyptic number.

18661951 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

18661951 is a deficient number, since it is larger than the sum of its proper divisors (4808897).

18661951 is an equidigital number, since it uses as much as digits as its factorization.

18661951 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2043 (or 2021 counting only the distinct ones).

The product of its digits is 12960, while the sum is 37.

The square root of 18661951 is about 4319.9480320948. The cubic root of 18661951 is about 265.2481406601.

The spelling of 18661951 in words is "eighteen million, six hundred sixty-one thousand, nine hundred fifty-one".