21869641 has 2 divisors, whose sum is σ = 21869642. Its totient is φ = 21869640.

The previous prime is 21869609. The next prime is 21869669. The reversal of 21869641 is 14696812.

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., 18966025 + 2903616 = 4355^2 + 1704^2 .

It is a cyclic number.

It is not a de Polignac number, because 21869641 - 2⁵ = 21869609 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21869641.

It is not a weakly prime, because it can be changed into another prime (21869041) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10934820 + 10934821.

It is an arithmetic number, because the mean of its divisors is an integer number (10934821).

Almost surely, 2^21869641 is an apocalyptic number.

It is an amenable number.

21869641 is a deficient number, since it is larger than the sum of its proper divisors (1).

21869641 is an equidigital number, since it uses as much as digits as its factorization.

21869641 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20736, while the sum is 37.

The square root of 21869641 is about 4676.4987971772. The cubic root of 21869641 is about 279.6493953540.

The spelling of 21869641 in words is "twenty-one million, eight hundred sixty-nine thousand, six hundred forty-one".