21640434 has 16 divisors (see below), whose sum is σ = 43443840. Its totient is φ = 7186320.

The previous prime is 21640427. The next prime is 21640441. The reversal of 21640434 is 43404612.

It is an interprime number because it is at equal distance from previous prime (21640427) and next prime (21640441).

It is a Curzon 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, 5029 + ... + 8280.

It is an arithmetic number, because the mean of its divisors is an integer number (2715240).

Almost surely, 2^21640434 is an apocalyptic number.

21640434 is an abundant number, since it is smaller than the sum of its proper divisors (21803406).

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

21640434 is a wasteful number, since it uses less digits than its factorization.

21640434 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13585.

The product of its (nonzero) digits is 2304, while the sum is 24.

The square root of 21640434 is about 4651.9279874048. The cubic root of 21640434 is about 278.6689976250.

The spelling of 21640434 in words is "twenty-one million, six hundred forty thousand, four hundred thirty-four".