21961901 has 4 divisors (see below), whose sum is σ = 23651292. Its totient is φ = 20272512.

The previous prime is 21961897. The next prime is 21961931. The reversal of 21961901 is 10916912.

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

It can be written as a sum of positive squares in 2 ways, for example, as 4405801 + 17556100 = 2099^2 + 4190^2 .

It is not a de Polignac number, because 21961901 - 2² = 21961897 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 (21961931) 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, 844676 + ... + 844701.

It is an arithmetic number, because the mean of its divisors is an integer number (5912823).

Almost surely, 2^21961901 is an apocalyptic number.

It is an amenable number.

21961901 is a deficient number, since it is larger than the sum of its proper divisors (1689391).

21961901 is a wasteful number, since it uses less digits than its factorization.

21961901 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1689390.

The product of its (nonzero) digits is 972, while the sum is 29.

The square root of 21961901 is about 4686.3526329119. The cubic root of 21961901 is about 280.0420897612.

The spelling of 21961901 in words is "twenty-one million, nine hundred sixty-one thousand, nine hundred one".