21663477 has 48 divisors (see below), whose sum is σ = 37240000. Its totient is φ = 12402720.

The previous prime is 21663437. The next prime is 21663497. The reversal of 21663477 is 77436612.

21663477 is a `hidden beast` number, since 2 + 16 + 634 + 7 + 7 = 666.

It is not a de Polignac number, because 21663477 - 2⁶ = 21663413 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21663427) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 61899 + ... + 62247.

Almost surely, 2^21663477 is an apocalyptic number.

21663477 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21663477 is a deficient number, since it is larger than the sum of its proper divisors (15576523).

21663477 is a wasteful number, since it uses less digits than its factorization.

21663477 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 399 (or 382 counting only the distinct ones).

The product of its digits is 42336, while the sum is 36.

The square root of 21663477 is about 4654.4040434840. The cubic root of 21663477 is about 278.7678725964.

The spelling of 21663477 in words is "twenty-one million, six hundred sixty-three thousand, four hundred seventy-seven".