21649963 has 2 divisors, whose sum is σ = 21649964. Its totient is φ = 21649962.

The previous prime is 21649961. The next prime is 21649967. The reversal of 21649963 is 36994612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21649963 - 2¹ = 21649961 is a prime.

Together with 21649961, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21649961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10824981 + 10824982.

It is an arithmetic number, because the mean of its divisors is an integer number (10824982).

Almost surely, 2^21649963 is an apocalyptic number.

21649963 is a deficient number, since it is larger than the sum of its proper divisors (1).

21649963 is an equidigital number, since it uses as much as digits as its factorization.

21649963 is an evil number, because the sum of its binary digits is even.

The product of its digits is 69984, while the sum is 40.

The square root of 21649963 is about 4652.9520736840. The cubic root of 21649963 is about 278.7098940201.

The spelling of 21649963 in words is "twenty-one million, six hundred forty-nine thousand, nine hundred sixty-three".