21405974 has 4 divisors (see below), whose sum is σ = 32108964. Its totient is φ = 10702986.

The previous prime is 21405961. The next prime is 21405997. The reversal of 21405974 is 47950412.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21405974.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5351492 + ... + 5351495.

It is an arithmetic number, because the mean of its divisors is an integer number (8027241).

Almost surely, 2^21405974 is an apocalyptic number.

21405974 is a deficient number, since it is larger than the sum of its proper divisors (10702990).

21405974 is a wasteful number, since it uses less digits than its factorization.

21405974 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10702989.

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 21405974 is about 4626.6590537882. The cubic root of 21405974 is about 277.6589420335.

The spelling of 21405974 in words is "twenty-one million, four hundred five thousand, nine hundred seventy-four".