21481951 has 4 divisors (see below), whose sum is σ = 22612600. Its totient is φ = 20351304.

The previous prime is 21481949. The next prime is 21481963. The reversal of 21481951 is 15918412.

It is a happy number.

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 21481951 - 2¹ = 21481949 is a prime.

It is a super-2 number, since 2×21481951² = 922948437532802, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21481921) 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, 565296 + ... + 565333.

It is an arithmetic number, because the mean of its divisors is an integer number (5653150).

Almost surely, 2^21481951 is an apocalyptic number.

21481951 is a deficient number, since it is larger than the sum of its proper divisors (1130649).

21481951 is a wasteful number, since it uses less digits than its factorization.

21481951 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1130648.

The product of its digits is 2880, while the sum is 31.

The square root of 21481951 is about 4634.8625653842. The cubic root of 21481951 is about 277.9870557953.

The spelling of 21481951 in words is "twenty-one million, four hundred eighty-one thousand, nine hundred fifty-one".