21090007 has 2 divisors, whose sum is σ = 21090008. Its totient is φ = 21090006.

The previous prime is 21089993. The next prime is 21090061. The reversal of 21090007 is 70009012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21090007 - 2⁷ = 21089879 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21090067) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10545003 + 10545004.

It is an arithmetic number, because the mean of its divisors is an integer number (10545004).

Almost surely, 2^21090007 is an apocalyptic number.

21090007 is a deficient number, since it is larger than the sum of its proper divisors (1).

21090007 is an equidigital number, since it uses as much as digits as its factorization.

21090007 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 126, while the sum is 19.

The square root of 21090007 is about 4592.3857634132. The cubic root of 21090007 is about 276.2860185218.

Adding to 21090007 its reverse (70009012), we get a palindrome (91099019).

The spelling of 21090007 in words is "twenty-one million, ninety thousand, seven".