21730636 has 12 divisors (see below), whose sum is σ = 38746512. Its totient is φ = 10660208.

The previous prime is 21730559. The next prime is 21730637. The reversal of 21730636 is 63603712.

It is not an unprimeable number, because it can be changed into a prime (21730637) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 51040 + ... + 51463.

It is an arithmetic number, because the mean of its divisors is an integer number (3228876).

Almost surely, 2^21730636 is an apocalyptic number.

It is an amenable number.

21730636 is a deficient number, since it is larger than the sum of its proper divisors (17015876).

21730636 is a wasteful number, since it uses less digits than its factorization.

21730636 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 102560 (or 102558 counting only the distinct ones).

The product of its (nonzero) digits is 4536, while the sum is 28.

The square root of 21730636 is about 4661.6130255524. The cubic root of 21730636 is about 279.0556450892.

It can be divided in two parts, 21730 and 636, that added together give a triangular number (22366 = T₂₁₁).

The spelling of 21730636 in words is "twenty-one million, seven hundred thirty thousand, six hundred thirty-six".