18961640 has 32 divisors (see below), whose sum is σ = 43065000. Its totient is φ = 7513344.

The previous prime is 18961619. The next prime is 18961643. The reversal of 18961640 is 4616981.

It can be written as a sum of positive squares in 4 ways, for example, as 11464996 + 7496644 = 3386^2 + 2738^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 18961640.

It is not an unprimeable number, because it can be changed into a prime (18961643) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2186 + ... + 6534.

Almost surely, 2^18961640 is an apocalyptic number.

18961640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18961640 is an abundant number, since it is smaller than the sum of its proper divisors (24103360).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18961640 is a wasteful number, since it uses less digits than its factorization.

18961640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4469 (or 4465 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 35.

The square root of 18961640 is about 4354.4965265803. The cubic root of 18961640 is about 266.6604651336.

The spelling of 18961640 in words is "eighteen million, nine hundred sixty-one thousand, six hundred forty".