21642945 has 8 divisors (see below), whose sum is σ = 34628736. Its totient is φ = 11542896.

The previous prime is 21642941. The next prime is 21642949. The reversal of 21642945 is 54924612.

It is an interprime number because it is at equal distance from previous prime (21642941) and next prime (21642949).

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21642945 - 2² = 21642941 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21642941) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 721417 + ... + 721446.

It is an arithmetic number, because the mean of its divisors is an integer number (4328592).

Almost surely, 2^21642945 is an apocalyptic number.

It is an amenable number.

21642945 is a deficient number, since it is larger than the sum of its proper divisors (12985791).

21642945 is a wasteful number, since it uses less digits than its factorization.

21642945 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1442871.

The product of its digits is 17280, while the sum is 33.

The square root of 21642945 is about 4652.1978676750. The cubic root of 21642945 is about 278.6797754556.

The spelling of 21642945 in words is "twenty-one million, six hundred forty-two thousand, nine hundred forty-five".