21663532 has 24 divisors (see below), whose sum is σ = 41746320. Its totient is φ = 9754560.

The previous prime is 21663527. The next prime is 21663547. The reversal of 21663532 is 23536612.

It is a self number, because there is not a number n which added to its sum of digits gives 21663532.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2538 + ... + 7054.

It is an arithmetic number, because the mean of its divisors is an integer number (1739430).

Almost surely, 2^21663532 is an apocalyptic number.

21663532 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

21663532 is a deficient number, since it is larger than the sum of its proper divisors (20082788).

21663532 is a wasteful number, since it uses less digits than its factorization.

21663532 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4641 (or 4639 counting only the distinct ones).

The product of its digits is 6480, while the sum is 28.

The square root of 21663532 is about 4654.4099518629. The cubic root of 21663532 is about 278.7681085114.

Subtracting 21663532 from its reverse (23536612), we obtain a triangular number (1873080 = T₁₉₃₅).

The spelling of 21663532 in words is "twenty-one million, six hundred sixty-three thousand, five hundred thirty-two".