21940421 has 8 divisors (see below), whose sum is σ = 24454080. Its totient is φ = 19562688.

The previous prime is 21940409. The next prime is 21940427. The reversal of 21940421 is 12404912.

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

It is a cyclic number.

It is not a de Polignac number, because 21940421 - 2¹⁸ = 21678277 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21940427) 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, 33641 + ... + 34286.

It is an arithmetic number, because the mean of its divisors is an integer number (3056760).

Almost surely, 2^21940421 is an apocalyptic number.

It is an amenable number.

21940421 is a deficient number, since it is larger than the sum of its proper divisors (2513659).

21940421 is a wasteful number, since it uses less digits than its factorization.

21940421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 67963.

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 21940421 is about 4684.0603113111. The cubic root of 21940421 is about 279.9507608994.

The spelling of 21940421 in words is "twenty-one million, nine hundred forty thousand, four hundred twenty-one".