21652561 has 8 divisors (see below), whose sum is σ = 25251200. Its totient is φ = 18559044.

The previous prime is 21652537. The next prime is 21652639. The reversal of 21652561 is 16525612.

It is a de Polignac number, because none of the positive numbers 2^k-21652561 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21652061) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 31221 + ... + 31906.

It is an arithmetic number, because the mean of its divisors is an integer number (3156400).

Almost surely, 2^21652561 is an apocalyptic number.

It is an amenable number.

21652561 is a deficient number, since it is larger than the sum of its proper divisors (3598639).

21652561 is an frugal number, since it uses more digits than its factorization.

21652561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 63148 (or 63134 counting only the distinct ones).

The product of its digits is 3600, while the sum is 28.

The square root of 21652561 is about 4653.2312429107. The cubic root of 21652561 is about 278.7210419890.

The spelling of 21652561 in words is "twenty-one million, six hundred fifty-two thousand, five hundred sixty-one".