21021697 has 2 divisors, whose sum is σ = 21021698. Its totient is φ = 21021696.

The previous prime is 21021683. The next prime is 21021703. The reversal of 21021697 is 79612012.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14447601 + 6574096 = 3801^2 + 2564^2 .

It is a cyclic number.

It is not a de Polignac number, because 21021697 - 2⁷ = 21021569 is a prime.

It is not a weakly prime, because it can be changed into another prime (21021617) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510848 + 10510849.

It is an arithmetic number, because the mean of its divisors is an integer number (10510849).

Almost surely, 2^21021697 is an apocalyptic number.

It is an amenable number.

21021697 is a deficient number, since it is larger than the sum of its proper divisors (1).

21021697 is an equidigital number, since it uses as much as digits as its factorization.

21021697 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1512, while the sum is 28.

The square root of 21021697 is about 4584.9424205763. The cubic root of 21021697 is about 275.9874014063.

The spelling of 21021697 in words is "twenty-one million, twenty-one thousand, six hundred ninety-seven".