18521407 has 2 divisors, whose sum is σ = 18521408. Its totient is φ = 18521406.

The previous prime is 18521329. The next prime is 18521411. The reversal of 18521407 is 70412581.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-18521407 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (18521467) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 9260703 + 9260704.

It is an arithmetic number, because the mean of its divisors is an integer number (9260704).

Almost surely, 2^18521407 is an apocalyptic number.

18521407 is a deficient number, since it is larger than the sum of its proper divisors (1).

18521407 is an equidigital number, since it uses as much as digits as its factorization.

18521407 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 2240, while the sum is 28.

The square root of 18521407 is about 4303.6504272536. The cubic root of 18521407 is about 264.5805968152.

Adding to 18521407 its reverse (70412581), we get a palindrome (88933988).

The spelling of 18521407 in words is "eighteen million, five hundred twenty-one thousand, four hundred seven".