21400971 has 16 divisors (see below), whose sum is σ = 30471936. Its totient is φ = 13327776.

The previous prime is 21400949. The next prime is 21400979. The reversal of 21400971 is 17900412.

It is not a de Polignac number, because 21400971 - 2⁹ = 21400459 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21400979) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 640 + ... + 6573.

It is an arithmetic number, because the mean of its divisors is an integer number (1904496).

Almost surely, 2^21400971 is an apocalyptic number.

21400971 is a deficient number, since it is larger than the sum of its proper divisors (9070965).

21400971 is a wasteful number, since it uses less digits than its factorization.

21400971 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7282.

The product of its (nonzero) digits is 504, while the sum is 24.

The square root of 21400971 is about 4626.1183512746. The cubic root of 21400971 is about 277.6373088837.

The spelling of 21400971 in words is "twenty-one million, four hundred thousand, nine hundred seventy-one".