21940069 has 4 divisors (see below), whose sum is σ = 21958380. Its totient is φ = 21921760.

The previous prime is 21940067. The next prime is 21940073. The reversal of 21940069 is 96004912.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 19909444 + 2030625 = 4462^2 + 1425^2 .

It is a cyclic number.

It is not a de Polignac number, because 21940069 - 2¹ = 21940067 is a prime.

It is a super-2 number, since 2×21940069² = 962733255449522, which contains 22 as substring.

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 Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21940069.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21940063) 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, 7222 + ... + 9799.

It is an arithmetic number, because the mean of its divisors is an integer number (5489595).

Almost surely, 2^21940069 is an apocalyptic number.

It is an amenable number.

21940069 is a deficient number, since it is larger than the sum of its proper divisors (18311).

21940069 is a wasteful number, since it uses less digits than its factorization.

21940069 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18310.

The product of its (nonzero) digits is 3888, while the sum is 31.

The square root of 21940069 is about 4684.0227369218. The cubic root of 21940069 is about 279.9492637663.

The spelling of 21940069 in words is "twenty-one million, nine hundred forty thousand, sixty-nine".