21640974 has 8 divisors (see below), whose sum is σ = 43281960. Its totient is φ = 7213656.

The previous prime is 21640963. The next prime is 21640979. The reversal of 21640974 is 47904612.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

21640974 is an admirable number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21640979) 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, 1803409 + ... + 1803420.

It is an arithmetic number, because the mean of its divisors is an integer number (5410245).

Almost surely, 2^21640974 is an apocalyptic number.

21640974 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21640974 is a wasteful number, since it uses less digits than its factorization.

21640974 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3606834.

The product of its (nonzero) digits is 12096, while the sum is 33.

The square root of 21640974 is about 4651.9860274941. The cubic root of 21640974 is about 278.6713155084.

The spelling of 21640974 in words is "twenty-one million, six hundred forty thousand, nine hundred seventy-four".