21490687 has 2 divisors, whose sum is σ = 21490688. Its totient is φ = 21490686.

The previous prime is 21490663. The next prime is 21490697. The reversal of 21490687 is 78609412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21490687 - 2²³ = 13102079 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21490627) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10745343 + 10745344.

It is an arithmetic number, because the mean of its divisors is an integer number (10745344).

Almost surely, 2^21490687 is an apocalyptic number.

21490687 is a deficient number, since it is larger than the sum of its proper divisors (1).

21490687 is an equidigital number, since it uses as much as digits as its factorization.

21490687 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 24192, while the sum is 37.

The square root of 21490687 is about 4635.8048923569. The cubic root of 21490687 is about 278.0247334066.

The spelling of 21490687 in words is "twenty-one million, four hundred ninety thousand, six hundred eighty-seven".