21020651 has 2 divisors, whose sum is σ = 21020652. Its totient is φ = 21020650.

The previous prime is 21020641. The next prime is 21020683. The reversal of 21020651 is 15602012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21020651 - 2¹⁰ = 21019627 is a prime.

It is not a weakly prime, because it can be changed into another prime (21020611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510325 + 10510326.

It is an arithmetic number, because the mean of its divisors is an integer number (10510326).

Almost surely, 2^21020651 is an apocalyptic number.

21020651 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020651 is an equidigital number, since it uses as much as digits as its factorization.

21020651 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 120, while the sum is 17.

The square root of 21020651 is about 4584.8283501130. The cubic root of 21020651 is about 275.9828237928.

Adding to 21020651 its reverse (15602012), we get a palindrome (36622663).

The spelling of 21020651 in words is "twenty-one million, twenty thousand, six hundred fifty-one".