402100021 has 4 divisors (see below), whose sum is σ = 423263200. Its totient is φ = 380936844.

The previous prime is 402099989. The next prime is 402100033. The reversal of 402100021 is 120001204.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 402100021 - 2⁵ = 402099989 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 402099980 and 402100007.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (402100081) 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, 10581561 + ... + 10581598.

It is an arithmetic number, because the mean of its divisors is an integer number (105815800).

Almost surely, 2^402100021 is an apocalyptic number.

It is an amenable number.

402100021 is a deficient number, since it is larger than the sum of its proper divisors (21163179).

402100021 is a wasteful number, since it uses less digits than its factorization.

402100021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21163178.

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

The square root of 402100021 is about 20052.4317976648. The cubic root of 402100021 is about 738.0934736909.

Adding to 402100021 its reverse (120001204), we get a palindrome (522101225).

The spelling of 402100021 in words is "four hundred two million, one hundred thousand, twenty-one".