21640026 has 16 divisors (see below), whose sum is σ = 43524000. Its totient is φ = 7172688.

The previous prime is 21640013. The next prime is 21640039. The reversal of 21640026 is 62004612.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21640013) and next prime (21640039).

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21639984 and 21640011.

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, 9001 + ... + 11148.

It is an arithmetic number, because the mean of its divisors is an integer number (2720250).

Almost surely, 2^21640026 is an apocalyptic number.

21640026 is an abundant number, since it is smaller than the sum of its proper divisors (21883974).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21640026 is a wasteful number, since it uses less digits than its factorization.

21640026 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20333.

The product of its (nonzero) digits is 576, while the sum is 21.

The square root of 21640026 is about 4651.8841344126. The cubic root of 21640026 is about 278.6672463098.

Adding to 21640026 its reverse (62004612), we get a palindrome (83644638).

The spelling of 21640026 in words is "twenty-one million, six hundred forty thousand, twenty-six".