21951047 has 4 divisors (see below), whose sum is σ = 22085880. Its totient is φ = 21816216.

The previous prime is 21951043. The next prime is 21951067. The reversal of 21951047 is 74015912.

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

It is a cyclic number.

It is not a de Polignac number, because 21951047 - 2² = 21951043 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21951043) 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, 67172 + ... + 67497.

It is an arithmetic number, because the mean of its divisors is an integer number (5521470).

Almost surely, 2^21951047 is an apocalyptic number.

21951047 is a deficient number, since it is larger than the sum of its proper divisors (134833).

21951047 is a wasteful number, since it uses less digits than its factorization.

21951047 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 134832.

The product of its (nonzero) digits is 2520, while the sum is 29.

The square root of 21951047 is about 4685.1944463384. The cubic root of 21951047 is about 279.9959480706.

Adding to 21951047 its reverse (74015912), we get a palindrome (95966959).

The spelling of 21951047 in words is "twenty-one million, nine hundred fifty-one thousand, forty-seven".