21652661 has 2 divisors, whose sum is σ = 21652662. Its totient is φ = 21652660.

The previous prime is 21652643. The next prime is 21652681. The reversal of 21652661 is 16625612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21022225 + 630436 = 4585^2 + 794^2 .

It is a cyclic number.

It is not a de Polignac number, because 21652661 - 2¹⁸ = 21390517 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21652681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10826330 + 10826331.

It is an arithmetic number, because the mean of its divisors is an integer number (10826331).

Almost surely, 2^21652661 is an apocalyptic number.

It is an amenable number.

21652661 is a deficient number, since it is larger than the sum of its proper divisors (1).

21652661 is an equidigital number, since it uses as much as digits as its factorization.

21652661 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4320, while the sum is 29.

The square root of 21652661 is about 4653.2419881197. The cubic root of 21652661 is about 278.7214710693.

The spelling of 21652661 in words is "twenty-one million, six hundred fifty-two thousand, six hundred sixty-one".