21001405 has 8 divisors (see below), whose sum is σ = 25334784. Its totient is φ = 16712400.

The previous prime is 21001399. The next prime is 21001411. The reversal of 21001405 is 50410012.

It is an interprime number because it is at equal distance from previous prime (21001399) and next prime (21001411).

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

It is not a de Polignac number, because 21001405 - 2³ = 21001397 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10041 + ... + 11950.

It is an arithmetic number, because the mean of its divisors is an integer number (3166848).

Almost surely, 2^21001405 is an apocalyptic number.

It is an amenable number.

21001405 is a deficient number, since it is larger than the sum of its proper divisors (4333379).

21001405 is a wasteful number, since it uses less digits than its factorization.

21001405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 22187.

The product of its (nonzero) digits is 40, while the sum is 13.

The square root of 21001405 is about 4582.7289904597. The cubic root of 21001405 is about 275.8985703397.

Adding to 21001405 its reverse (50410012), we get a palindrome (71411417).

The spelling of 21001405 in words is "twenty-one million, one thousand, four hundred five".