21402001 has 8 divisors (see below), whose sum is σ = 21714984. Its totient is φ = 21091200.

The previous prime is 21401993. The next prime is 21402013. The reversal of 21402001 is 10020412.

It can be written as a sum of positive squares in 4 ways, for example, as 8614225 + 12787776 = 2935^2 + 3576^2 .

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 21402001 - 2³ = 21401993 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21402091) 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, 31275 + ... + 31951.

It is an arithmetic number, because the mean of its divisors is an integer number (2714373).

Almost surely, 2^21402001 is an apocalyptic number.

It is an amenable number.

21402001 is a deficient number, since it is larger than the sum of its proper divisors (312983).

21402001 is a wasteful number, since it uses less digits than its factorization.

21402001 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1091.

The product of its (nonzero) digits is 16, while the sum is 10.

The square root of 21402001 is about 4626.2296743677. The cubic root of 21402001 is about 277.6417629159.

Adding to 21402001 its reverse (10020412), we get a palindrome (31422413).

The spelling of 21402001 in words is "twenty-one million, four hundred two thousand, one".