21457961 has 12 divisors (see below), whose sum is σ = 26053248. Its totient is φ = 17308992.

The previous prime is 21457957. The next prime is 21457963. The reversal of 21457961 is 16975412.

It is not a de Polignac number, because 21457961 - 2² = 21457957 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21457963) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3281 + ... + 7326.

It is an arithmetic number, because the mean of its divisors is an integer number (2171104).

Almost surely, 2^21457961 is an apocalyptic number.

It is an amenable number.

21457961 is a deficient number, since it is larger than the sum of its proper divisors (4595287).

21457961 is a wasteful number, since it uses less digits than its factorization.

21457961 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10648 (or 10631 counting only the distinct ones).

The product of its digits is 15120, while the sum is 35.

The square root of 21457961 is about 4632.2738476908. The cubic root of 21457961 is about 277.8835364345.

The spelling of 21457961 in words is "twenty-one million, four hundred fifty-seven thousand, nine hundred sixty-one".