21634649 has 2 divisors, whose sum is σ = 21634650. Its totient is φ = 21634648.

The previous prime is 21634637. The next prime is 21634661. The reversal of 21634649 is 94643612.

It is a balanced prime because it is at equal distance from previous prime (21634637) and next prime (21634661).

It can be written as a sum of positive squares in only one way, i.e., 14707225 + 6927424 = 3835^2 + 2632^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21634649 is a prime.

It is not a weakly prime, because it can be changed into another prime (21634699) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10817324 + 10817325.

It is an arithmetic number, because the mean of its divisors is an integer number (10817325).

Almost surely, 2^21634649 is an apocalyptic number.

It is an amenable number.

21634649 is a deficient number, since it is larger than the sum of its proper divisors (1).

21634649 is an equidigital number, since it uses as much as digits as its factorization.

21634649 is an evil number, because the sum of its binary digits is even.

The product of its digits is 31104, while the sum is 35.

The square root of 21634649 is about 4651.3061606392. The cubic root of 21634649 is about 278.6441638067.

The spelling of 21634649 in words is "twenty-one million, six hundred thirty-four thousand, six hundred forty-nine".