21290747 has 2 divisors, whose sum is σ = 21290748. Its totient is φ = 21290746.

The previous prime is 21290743. The next prime is 21290761. The reversal of 21290747 is 74709212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21290747 - 2² = 21290743 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is not a weakly prime, because it can be changed into another prime (21290743) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10645373 + 10645374.

It is an arithmetic number, because the mean of its divisors is an integer number (10645374).

Almost surely, 2^21290747 is an apocalyptic number.

21290747 is a deficient number, since it is larger than the sum of its proper divisors (1).

21290747 is an equidigital number, since it uses as much as digits as its factorization.

21290747 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7056, while the sum is 32.

The square root of 21290747 is about 4614.1897446897. The cubic root of 21290747 is about 277.1598385887.

Adding to 21290747 its reverse (74709212), we get a palindrome (95999959).

The spelling of 21290747 in words is "twenty-one million, two hundred ninety thousand, seven hundred forty-seven".