21643942 has 4 divisors (see below), whose sum is σ = 32465916. Its totient is φ = 10821970.

The previous prime is 21643939. The next prime is 21643961. The reversal of 21643942 is 24934612.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5410984 + ... + 5410987.

It is an arithmetic number, because the mean of its divisors is an integer number (8116479).

Almost surely, 2^21643942 is an apocalyptic number.

21643942 is a deficient number, since it is larger than the sum of its proper divisors (10821974).

21643942 is a wasteful number, since it uses less digits than its factorization.

21643942 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10821973.

The product of its digits is 10368, while the sum is 31.

The square root of 21643942 is about 4652.3050200949. The cubic root of 21643942 is about 278.6840545939.

The spelling of 21643942 in words is "twenty-one million, six hundred forty-three thousand, nine hundred forty-two".