21890401 has 6 divisors (see below), whose sum is σ = 23703990. Its totient is φ = 20206368.

The previous prime is 21890383. The next prime is 21890417. The reversal of 21890401 is 10409812.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 739600 + 21150801 = 860^2 + 4599^2 .

It is not a de Polignac number, because 21890401 - 2⁵ = 21890369 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21890461) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 64596 + ... + 64933.

It is an arithmetic number, because the mean of its divisors is an integer number (3950665).

Almost surely, 2^21890401 is an apocalyptic number.

It is an amenable number.

21890401 is a deficient number, since it is larger than the sum of its proper divisors (1813589).

21890401 is a wasteful number, since it uses less digits than its factorization.

21890401 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129555 (or 129542 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 21890401 is about 4678.7178799325. The cubic root of 21890401 is about 279.7378541362.

The spelling of 21890401 in words is "twenty-one million, eight hundred ninety thousand, four hundred one".