21945869 has 8 divisors (see below), whose sum is σ = 24393312. Its totient is φ = 19573840.

The previous prime is 21945863. The next prime is 21945871. The reversal of 21945869 is 96854912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21945869 - 2⁴ = 21945853 is a prime.

It is a super-2 number, since 2×21945869² = 963242332330322, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21945863) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 18239 + ... + 19404.

It is an arithmetic number, because the mean of its divisors is an integer number (3049164).

Almost surely, 2^21945869 is an apocalyptic number.

It is an amenable number.

21945869 is a deficient number, since it is larger than the sum of its proper divisors (2447443).

21945869 is a wasteful number, since it uses less digits than its factorization.

21945869 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 37707.

The product of its digits is 155520, while the sum is 44.

The square root of 21945869 is about 4684.6418219539. The cubic root of 21945869 is about 279.9739303960.

The spelling of 21945869 in words is "twenty-one million, nine hundred forty-five thousand, eight hundred sixty-nine".