21643450 has 12 divisors (see below), whose sum is σ = 40256910. Its totient is φ = 8657360.

The previous prime is 21643429. The next prime is 21643507. The reversal of 21643450 is 5434612.

It can be written as a sum of positive squares in 3 ways, for example, as 20457529 + 1185921 = 4523^2 + 1089^2 .

It is a Harshad number since it is a multiple of its sum of digits (25).

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 216385 + ... + 216484.

Almost surely, 2^21643450 is an apocalyptic number.

21643450 is a deficient number, since it is larger than the sum of its proper divisors (18613460).

21643450 is a wasteful number, since it uses less digits than its factorization.

21643450 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 432881 (or 432876 counting only the distinct ones).

The product of its (nonzero) digits is 2880, while the sum is 25.

The square root of 21643450 is about 4652.2521427799. The cubic root of 21643450 is about 278.6819429393.

The spelling of 21643450 in words is "twenty-one million, six hundred forty-three thousand, four hundred fifty".