21917643 has 32 divisors (see below), whose sum is σ = 33841152. Its totient is φ = 12487200.

The previous prime is 21917639. The next prime is 21917663. The reversal of 21917643 is 34671912.

It is not a de Polignac number, because 21917643 - 2² = 21917639 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is not an unprimeable number, because it can be changed into a prime (21917633) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 50638 + ... + 51068.

It is an arithmetic number, because the mean of its divisors is an integer number (1057536).

Almost surely, 2^21917643 is an apocalyptic number.

21917643 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

21917643 is a deficient number, since it is larger than the sum of its proper divisors (11923509).

21917643 is a wasteful number, since it uses less digits than its factorization.

21917643 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 535.

The product of its digits is 9072, while the sum is 33.

The square root of 21917643 is about 4681.6282423960. The cubic root of 21917643 is about 279.8538480459.

The spelling of 21917643 in words is "twenty-one million, nine hundred seventeen thousand, six hundred forty-three".